I found KVMs to be annoying and settled on a USB switch and letting my monitor auto-switch inputs.

My mouse felt laggy under the KVM because of the high polling rate it wanted to use. Some key combinations also got added delay because of the way the KVM listened to shortcuts.

Instead of the $200 KVM a $20 alternative with a dedicated switching button did what I wanted in a much better way. Maybe if you need to switch back and forth more often a KVM would be alright? But at that point I guess dedicated monitors with the USB switch would still be better.