Is the SSD being connected internally on a controller that shows up correctly under ESXi? One of the issues with using commodity parts (especially motherboards) is you could very well run into blocking issues with the hardware. One BIOS version might be great, but the one before and one after it breaks it.
If the drive simply never shows up in either the install, or once the host boots into ESXi, then it's a compatibility issue. It MIGHT be fixed with the needed drivers (injected either into the install ISO, or post install).
Personally, since ESXi loads into memory, I've not seen any performance gain from running on fast storage. ESXi on USB thumb drives have had no performance difference than ESXi installed onto higher speed hard drives. I am talking about on either the exact same host, or an identical host.
