Given a choice between the current database-level HA options for MySQL, like Master-Master, Cluster, or Galera, and vSphere HA for the machine running the MySQL master, which would you use or combine and why?
vSphere HA will not give you 100% uptime. If a host fails, all of the VMs that were running on that host will be restarted on another host, provided that there are enough resources (CPU & memory). If you want a higher uptime using vSphere, then you will want to look into Fault Tolerance. It essentially runs the VM on 2 hosts concurrently and therefore uses twice the CPU and memory as HA. However, if you are using Mysql master-master, cluster, etc. then you are probably using the same amount of resources as FT.
If you want to use Mysql master-master or cluster in a vSphere environment, then you can configure VMWare DRS rules to keep the guest VMs on separate hosts. This would be beneficial in case one of the hosts fails.