For most business applications, AWS vs Azure is a closer contest than either provider’s marketing suggests. Amazon Web Services (AWS) and Microsoft Azure both have data centres in the UK, both run Windows Server and SQL Server, and both charge by usage. The decision usually turns on things that have little to do with the technology: what your organisation already uses, which Microsoft licences you own, and which platform the people who will look after the system know best.
This comparison is written for a business moving an existing system off its own server, typically an application built on Microsoft’s .NET with a SQL Server database. It leaves out prices, which change often and depend on your licences. The only reliable way to compare cost is to have the same design priced on both.
What the two have in common
UK data centres. AWS has a London region made up of three availability zones, which are separate groups of data centres. Azure has UK South in London, also with three zones, and UK West in Cardiff. Either provider lets you keep a system and its backups in the UK.
Virtual servers and managed services. Both rent virtual servers that you run much as you run a server today. Both also offer managed services, where the provider looks after the operating system and the database software and you look after the application and its data.
Pay as you go, with discounts for commitment. Both charge for what is switched on, and both offer lower rates in return for a commitment of one or three years. Neither will stop you overspending. Our tips for reducing cloud hosting costs apply equally to each.
A shared responsibility for security. Both secure their buildings, hardware and networks, and both leave accounts, configuration and data to you. Software development in the cloud and its security obstacles explains where the line falls.
How they compare for a Microsoft-based system
| AWS | Azure | |
|---|---|---|
| UK regions | Europe (London) | UK South (London) and UK West (Cardiff) |
| Windows Server licences you already own | Can be brought only under narrow conditions, so most customers pay for the licence within the hourly rate | Azure Hybrid Benefit applies them to servers in Azure, if they carry Software Assurance or are subscription licences |
| Managed SQL Server | Amazon RDS for SQL Server | Azure SQL Database and Azure SQL Managed Instance |
| Platform service for hosting an ASP.NET web application | Elastic Beanstalk | App Service |
| Cost and sizing tools | Cost Explorer, Budgets, Compute Optimizer | Cost Management, Advisor |
| Administrator sign-in | IAM Identity Center, which can be connected to the directory you already use | Microsoft Entra ID, the same directory that sits behind Microsoft 365 |
Where Azure has the edge
Licences. For a system on Windows Server and SQL Server, licences are a large share of the running cost. With qualifying Windows Server licences, Azure Hybrid Benefit means paying only the base rate for the server, which is the same rate charged for a Linux server, and a similar benefit covers SQL Server licences. To qualify, the licences need active Software Assurance or to be subscription licences. If yours were bought outright without Software Assurance, the benefit does not apply and the gap between the two providers narrows.
It fits what a Microsoft-based business already has. If your staff sign in to Microsoft 365, their accounts are already in Microsoft Entra ID (the service formerly called Azure Active Directory), and the same accounts and sign-in rules can control access to Azure. A business whose IT support already manages Microsoft 365 has less that is new to learn.
An easy home for an existing SQL Server database. Azure SQL Managed Instance is designed to take an existing SQL Server database with few changes, and Microsoft describes it as offering “the broadest SQL Server engine compatibility”.
One advantage that people still quote has narrowed. For older versions, running an out-of-support SQL Server on an Azure virtual server brought the paid Extended Security Updates at no extra charge. Microsoft’s documentation on Extended Security Updates says that this no longer applies from SQL Server 2016, whose security fixes ended on 14 July 2026. Moving SQL Server 2016 to Azure does not by itself keep it patched.
Where AWS has the edge
You already use it. If another of your systems runs on AWS, or your developers and support company know it well, that familiarity is worth more than any item in a feature list. A well-run system on the platform your people understand is safer than a badly run one on the platform that looked better in a comparison.
The application does not need Windows. Software built on modern .NET, as distinct from the older .NET Framework, runs on Linux as well as Windows. If the database is also something other than SQL Server, there are no Microsoft licences in the picture, Azure’s licensing advantage disappears and the two providers compete on price and skills alone.
You hold no licences to bring. A business without Software Assurance pays for Windows Server and SQL Server within the hourly rate on either platform. Amazon RDS for SQL Server is sold this way, with AWS handling backups and software patching, and it is a sound choice for a database that needs to stay on SQL Server.
What the UK regulator has said
The Competition and Markets Authority (CMA) finished a market investigation into cloud services with a final decision on 31 July 2025. In its announcement of 31 March 2026 the CMA said the investigation had found that Amazon and Microsoft “have positions of significant market power”, and that it had identified limits to customer choice from the fees charged for moving data out, from barriers to using more than one provider, and from the licensing of Microsoft’s business software on the cloud. It reported that both companies had set out actions on data transfer fees and interoperability for UK customers, and that it would open an investigation into Microsoft’s business software.
For a buyer, the practical point is that the terms on licensing and on leaving are changing. Both providers already say that they will waive data transfer charges for a customer who is moving away entirely, subject to conditions. Ask for the current position in writing before you commit, and do not rely on an article for it, including this one.
Should you use both
For a business with one or two systems, no. Two platforms mean two sets of security settings to get right, two bills to watch and two bodies of knowledge to keep up. Using both makes sense only when something you depend on, such as a product bought from a supplier, already lives on the other one.
How to choose
- Find out what your organisation and its IT support company already use and know.
- Get your licence position in writing: which Windows Server and SQL Server licences you own, and whether they carry Software Assurance.
- Check whether the application needs Windows at all.
- Have the same design costed on both, including licences, backups and data transfer.
- Ask who will run the system after the move, and which platform they would choose.
Either platform will do the job for most business applications. When we plan a cloud migration we recommend one of the two and explain the reasoning, and you should expect the same of any supplier.