Same as VGA, shit just works, don’t need to worry about drivers or OS. So if your server shits the bed, you don’t need to worry about these things not working so you can can figure what went wrong.
I don’t know what server you’re running, but I have never had any issues with USB keyboards. They just work, including in the firmware. No drivers needed. Besides, a proper server motherboard will have IPMI so you can just remote into it.
I’ve had KVMs that don’t like the ‘fancier’ USB keyboards with NKRO. It would work, but it wouldn’t listen for its own ‘switch to different console’ hotkeys. Reconfiguring the keyboard to run in 6KRO-only mode addressed it, but not every keyboard can be configured that way.
In a server environment it’s perfect. Have multiple baremetal servers in the rack?
No problem, all you need is a PS/2 + VGA KVM and you can control them easily without fiddling. No protocol handshake, no HDCP in the way.
For most workflows, especially text, 720p is more than enough.
That said, DisplayPort >>>>> HDMI