Public cloud adoption has continued to gather pace in recent years, as more and more businesses move applications out of their data centres in a bid to cut costs and increase agility. 

This has fuelled a crowded infrastructure as a service (Iaas) market worth a total of $16.5 billion in 2015, according to Gartner stats.

And it is a market that has, thus far, largely been dominated by AWS. It has been estimated that, until recently, AWS has more than 10 times the compute capacity of its all of its 14 closest rivals combined – and that includes Microsoft Azure. Read next AWS: 10 defining moments for the cloud giant

But despite AWS’s dominance, Microsoft has continued to gain ground and it has built a huge global cloud network too. While not as big as AWS, it is around twice the scale of its nearest rival, says Gartner.

So what separates the two cloud providers? And how can you start to decide which Iaas platform is best-suited to your organisation?

Read next: Five key legal considerations when negotiating cloud contracts

Microsoft Azure vs Amazon AWS: Feature and services

Selecting one cloud over the other will come down to the wants and needs of each individual customer, and the workloads they are running. In fact it is often the case that organisations will use both providers within different parts of their operations, for different use cases.

However there are a number of differentiating factors that separate the approaches of the two firms, which can help end-users consider which is right for them.

It is worth starting by looking at the services offered by the two firms. Both AWS and Microsoft Azure offer similar capabilities to some degree, along the lines of compute, storage and networking.

They share the common elements of a public cloud: self-service and instant provisioning, autoscaling, plus security, compliance and identify management features.

Both companies also continually invest in meeting demand for new cloud services. This has resulted in more mature analytics offerings. For example, support for Hadoop clusters are provided by both AWS (Elastic Map Reduce) and Azure (HDInsight).

AWS and Microsoft have added machine learning tools and a number of features targeted at the Internet of Things, while customers can tap either cloud to variously build a mobile app or even create high performance computing environment depending on their needs.

Meanwhile the recent buzz around containers is catered for too, with both providers supporting Docker services. Microsoft has also been also been creating its own Hyper-V container technology that it will run in on-premise data centres as part of its forthcoming Windows Server 2016 release. Read next: What to expect from Windows Server 2016

Microsoft Azure vs Amazon AWS:  Compute, storage, databases and networking

It is often compute and storage that customers are most interested in.

For compute, AWS’ main offering is its EC2 instances, which can be tailored with a large number of options. It also provides related services such as Elastic Beanstalk for app deployment, the EC2 Container service, AWS Lambda and Autoscaling.

Meanwhile, Azure's compute offering is centred around its Virtual Machines (VMs), with other tools such as Cloud Services and Resource Manager to help deploy applications on the cloud, and its Azure Autoscaling service.

There are a couple of differentiating factors, according to Gartner, such as EC2 instances being billed by the hour as opposed to by the minute with Azure.

Also, while neither provider offers native support for VMware’s vSphere virtualisation, Azure’s interoperability with Hyper-V might offer some advantages for those running Microsoft’s virtual machines in their data centre, and for those using the Azure Stack private cloud system.

Both providers have similar storage options, says Gartner. 

AWS storage includes its Simple Storage (S3), Elastic Block Storage (EBS), Elastic File System (EFS), Import/Export large volume data transfer service, Glacier archive backup and Storage Gateway, which integrates with on-premise environments.

Microsoft’s offerings include its core Azure Storage service, Azure Blob block storage, as well as Table, Queue and File storage. It also offers Site Recovery, Import Export and Azure Backup.

The two cloud providers also offer “excellent” networking capabilities - according to Gartner's report 'Key Services Differences Between AWS and Azure' report - allowing applications to be deployed on a local or global level, relying on server load balancing components (Azure Load Balancer, and AWS’ Elastic Load Balancing), and direct network connectivity to link with on-premise systems.

Both support relational databases (Azure SQL Database, Amazon Relational Database Service and Redshift), and NoSQL data bases (Azure DocumentDB and Amazon DynamoDB).

Microsoft Azure vs Amazon AWS: Pricing

Pricing can be a huge attraction for those considering a move to the cloud, and for good reason: there has been a continued downward trend on prices for some time now. See also: Making sense of public cloud pricing: What does the cloud ‘pricing war’ mean for CIOs in 2016?

In general terms, prices are roughly comparable, with Microsoft pledging to keep pace with AWS’s price drops, which can often be the cheaper option. 

The hyper-competitiveness of cloud vendors has been hugely beneficial for customers, with frequent cuts to prices for various services. This is clearly good news for IT departments, often unexpectedly freeing up budgets as vendor margins get thinner.

Microsoft bucked this trend to some degree, and recently made changes to its pricing in line with currency fluctuations, but claimed that UK customers would not be affected.  Update 21/10/2016: Microsoft is increasing the price of its enterprise software and cloud services for UK customers, blaming the slumping value of the pound post-Brexit. Effective January 1 2017, on-premise enterprise software will increase by 13 percent and cloud prices by 22 percent for new customers. These changes will not affect existing licence holders.

Working out pricing can be complex, however. In particular AWS’ pricing structures are not always entirely clear, and some customers look to third parties to manage costs.  

AWS provides a price calculator here, as does Microsoft here.

Both vendors offer free introductory tiers, before beginning to charge customers.

Microsoft Azure vs AWS: Customers

A high-profile user base may not be the main reason for choosing either cloud provider. But it can help the more cautious organisations understand how the public cloud is benefitting others in their sector.  

This is clearly a strong-point of AWS. It has increasingly taken on large customer deals, leading to the intriguing situation of a company owned by what was once simply an online bookseller threatening to usurp some of the biggest names in IT.

For example, although the US Central Intelligence Agency eventually signed a contract with IBM, awarding AWS a contract to build its private cloud in a one-off deal in 2013 could be seen as symbolic of a change in mentality by buyers.

A major proponent of AWS has been Netflix - a longstanding customer which recently claimed it would soon be shutting the rest of its data centres in a final move to the cloud. But aside from web pioneers, its real success has been in convincing more traditional businesses to move to the cloud. Read next: How News Corp expects to save 'tens of millions of dollars' by moving to the AWS cloud

Other major customers include: AirBnB, Aon, Channel 4, Financial Times, Dow Jones, Kurt Geiger, Lonely Planet, Nasdaq, Nike, Nisa Retail, Pfizer, and the Royal Opera House. A full list of AWS customers can be seen here.

Microsoft perhaps has less high profile Azure users, with most of the messaging from the vendor appearing to be around its widely used Saas tools.

But the Redmond firm has also notched up some notable customer wins such as Pearson, Ford, NBC News, dunnhumby and Easyjet, to name but a few.

Read next: The Guardian goes all-in on AWS public cloud after OpenStack 'disaster’

Read next: How Tesco Bank has adopted AWS cloud as 'business as usual' in eight months

Read next: Shipping container firm Seaco migrates SAP platform to AWS cloud to improve ERP performance

Microsoft Azure vs AWS:  AWS pros and cons

As mentioned before, the reasons for picking one vendor over another will differ for each customer. But there are aspects of the competing clouds that will offer benefits in certain circumstances.

The breadth and depth of the AWS offering is seen as a plus for AWS.

Its cloud service has been around since way back in 2006, and it has build out enterprise-friendly services that will appeal to CIOs as well as development staff. Forrester’s ‘Enterprise Public Cloud Platforms, Q4 2014’ report, written by analysts John R. Rymer and James Staten, gives AWS the highest rating from a CIO perspective [the report also offers analysis for devops and coders].

The vendor ranks highest in many fields such as platform configuration options, monitoring and policy features, security, reliability as well as its service offerings. Its partner ecosystem and general product strategy are also second to none, according to Forrester, and its AWS Marketplace has a large number of third party software services.

Another of the benefits of the AWS cloud is its openness and flexibility.

For example, Transport for London - which also relies on Azure in other parts of its operations - has used AWS to meet spikes in demand for its online services such as its Journey Planner tool.

This predominantly means relying on EC2 instances to deploy a mixture of Windows machines, Linux machines and Linux web firewalls, as well as some S3 storage. The government agency also uses other AWS features such as Simple Email Service (SES), Simple Notification Service (SNS) for push notifications, Simple Queue Service (SQS), its Cloud Watch metrics tool and Route 53 Domain Name Server.

While TfL uses Azure in other parts of its business, such as its Oyster card service, it chose AWS as it met the requirements for its online services.

"When we were looking at the cloud providers and the technology stack we decided we were going to go for was actually a mixture of Microsoft and non-Microsoft products," says Dan Mewett, solution architect for Transport for London.

"AWS at the time was one of the only providers that easily allowed that kind of 'pick and choose' to build the solution how you wanted it."

He adds that AWS makes it easier to use open source tools that run on Linux third party tools such as web accelerator Varnish Cache.

"That is the prime difference: that you can have exactly what you want from AWS – you will probably have to invest a little bit to build it – versus you can get the Microsoft stack on Azure very easily but if you want to go around that it is a bit more tricky."

However, one area AWS falls short to some degree is with its hybrid cloud strategy. Unlike Microsoft, AWS has tended to be dismissive of the benefits of on-premise private clouds. Many organisations prefer to keep sensitive data within their own data centres - such as those in the financial sector - using public clouds for other purposes. 

At the same time, this clearly has not deterred many customers from using AWS as part of their cloud strategy, regardless of whether they plan to move all systems to the cloud or not.

Another downside to AWS is the scale of its offering. While this is an attraction in many senses, it can be difficuly at times to navigate the large numbers of features that are on offer, and some see AWS as being a complex vendor to manage.

Microsoft Azure vs Amazon AWS: Azure pros and cons

Although it falls short of Amazon in many respects as part of Forrester’s scoring, it still rates highly in most aspects of its offering, and is generally better perceived than other cloud competitors. Also, the analyst firm rates it higher than AWS in certain areas such as development and testing tools, for example.

And the big pull for Azure is clearly where Microsoft already has a strong footing within an organisation.

Azure links well with key Microsoft on-premise systems such as Windows Server, System Center and Active Directory.

In addition, while both AWS and Azure have PaaS capabilities, this is a particular strength of Microsoft’s.

One of the downsides however has been a series of outages in recent months and years. Gartner analyst Lydia Leong has recommended considering disaster recovery capabilities away from Azure for critical applications hosted in the cloud.

Also, where AWS provides users with many options for supporting other platforms, Azure can be somewhat restrictive in comparison.

If you want to run anything other than Windows Server then Azure might not be the best solution. While Microsoft claims to have embraced open source platforms, it currently only provides ‘limited’ support for Linux operating systems.

Microsoft Azure vs Amazon AWS: Verdict

In very general terms, AWS appears be superior in terms of offering the widest range of functionality and most mature cloud offering. It has been suggested that it has a multi-year lead over its rivals in this respect.

Its expansive list of tools and services, along with its enterprise-friendly features make it a strong proposition for large organisations.  Meanwhile its huge - and continuously growing - infrastructure provides economies of scale that enable price cuts.

But it appears that Microsoft has begun to bridge the gap between the two, and will continue to do so with its ongoing investment in building out the Azure cloud platform and plans to strengthen ties with its on-premise software.  

For those organisations which are already invested heavily in Microsoft in terms of technology and developer skills - of which there are undoubtedly many - Microsoft Azure will continue to be a strong proposition.