>>> Command View says I have 4 TB left and VMware shows 44 TB.
With thin LUNs presented to the ESXi hosts, the provisioned LUN size shows up in vSphere. Unless there's a storage plugin installed in vSphere which is able to retrieve the physical (real) free disk space on the storage, the only place to see the usage is the storage system (e.g. Command View) itself. So that's what needs to be monitored.
André