For high performance OLTP SQL Server workloads, the memory optimized type of Azure VMs is usually the best choice. According to Microsoft, “Memory optimized VM sizes offer a high memory-to-CPU ratio that are great for relational database servers.” This gives you lower core counts, with more memory, which is usually what you want for SQL Server, to minimize your license costs and still have good performance.
You can go even further down this path with Constrained vCPU capable VM sizes, where you can constrain the VM vCPU count (to one half or one quarter of the original VM size) to reduce the cost of SQL Server licensing, while maintaining the same memory, storage, and I/O bandwidth as a non-constrained VM. These constrained Azure VMs have a suffix in the name that indicates the number of active vCPUs in the VM.
Click through for the comparison.