Pass-Through Disks are limited for VM mobility but as Garth points out the snapshot is direct for the data volume (eg. SQL Server MDF/NDF/LDFs) without snapshotting the entire VM volume store. When creating VMs there are Gen1 and Gen2. Gen1 supports VHD and VHDX, Gen2 only VHDX. Another advantage of VHDX is
There are cases when VHDs are required based application requirements. Example, there are some services in Azure that still require VHDs. VHDs are limited to 2TB whereas VHDX support up to 64TB.
Depending on whether the customer requires disk expansion for individual VMs then VHDX is far superior and provides live-resizing. Performance between VHDX and Pass-through Disks is minimal. Windows 2008 R2 VHDs were preferred over PTDs for performance but with Windows 2012 R2 VHDX vs PTD performance is negligible.
Also if they are VHDs today then can convert to VHDXs over time as an option.