Azure SQL Database (PaaS): automatic patching, backups, scaling, high availability baked in.
SQL Server on Azure VMs (IaaS): full OS control for legacy features, custom agents, or special drivers.
Decision matrix
PaaS for modern apps, elastic scale, cost predictability.
IaaS for OS-level dependencies, SSIS/SSRS custom setups, niche extensions.
Cost & ops
PaaS reduces admin toil (HA, tuning, updates). IaaS offers freedom—but you own resilience.
Bottom line
Greenfield? Start PaaS. Lift-and-shift? Begin IaaS, plan a managed migration path.