Hi Andy, that's a great question, thanks for asking.
SQL FCI solution described above is an IaaS solution and is preferred by customers looking for the full control on the platform. With SQL FCI on Azure IaaS, customers get access to the VM, can choose any Azure VM family and size, customize storage configuration (ex: Premium SSD or Ultra Disk), install other apps that should run on the same VM with SQL Server, choose the SQL Server version and edition and also customize installation and configuration of SQL Server. if none of these are a requirement but you are looking for a high performance HA solution for SQL instance, then Azure SQL Managed Instance is the right deployment type, where you do not need to deal with clustering or any other aspect of platform management. Azure SQL MI is a PaaS service and Microsoft manages the platform hosting SQL instance, it offers much more benefits in addition to HA and performance at the instance level like patching service, automated backups, auto-failover groups for Geo-DR, threat protection, vulnerability assessment and data masking and more, please refer here for full list. Thanks,