I believe the polling rate on usb keyboards might be slower than ps2. It’s why some gaming motherboards still have ps2 inputs to this day.
EDIT: Actually, just read a bit more about this and ps2 is interrupt driven, so it responds when a key is pressed instead of polling 1000 times per second like usb. Some would say that these days latency is not a great concern with 1kHz usb polling rate.