Industry leading hypervisor - for good reason!

Comparing ESXi to the other big three hypervisors, VMWare ultimately comes out on top. Initially, we built our server farm on top of XenServer for a few years, since it was stable and everyone was already somewhat familiar with it. However, given the recent drama with XenServer and its licensing issues, we ran into a few hurdles. We moved over to the open-sourced XenServer [which follows the main release pretty closely], but had issues not only with certain Windows VM's perpetually crashing on known good hardware, but also certain feature support like GPU virtualization and USB-passthrough. We eventually made the switch to VMWare ESXi as that's what our team had been running in their home-labs to diversify their experience. We did not experience any of the same issues under ESXi as we had on XenServer and the features we were looking for were all there and easy to use.

Hyper-V runs on Windows Server and was considered to be way too heavy to use in a reasonable way. Proxmox was ultimately written off for being a solely community support kind of hypervisor and is somewhat regarded as only the enthusiast hypervisor, not completely professional.