One pretty big one, if you're looking at homelab use, is that Proxmox is just Debian, so it's waaaay more likely to run on crap-tier commodity hardware, whereas VMware has all the usual enterprise-level support commitments and so you're very much on your own if you try to force it to run on hardware that isn't on their official compatibility list.
That was my first (and last) hurdle when wanting to try out ESXi...
I booted up the installer only to be greeted by a "not enough RAM" message. I believe it's 4GB minimum, which my tiny machine had, but ESXi read it as 3.9GB instead of 4.0GB and refused to budge.
Very happy with Proxmox on the other hand! Having access to the underlying Debian is also quite nice if you need to do something that's not supported by the interface.
The ZFS Filesystem is a nice feature
These were what i was thinking of yeah.