QUOTE(XaeL @ Jun 22 2012, 05:41 AM)
Ps/2 uses interrupts.
USB uses polling.
USB @ 1000hz is still slower than interrupts due to the fact that keyboard interrupts take less than 1ms to notify the relevant hardware controller.
This is true as far as it goes, but 1000 polls a second is a bit overkill when the game only cares about every 1/60th of a second...
In short, you're not likely to notice or care - but if it makes you feel better PS/2 is technically advantageous, probably.
Note: interrupts may take priority on the system bus but that doesn't mean that they aren't queued up as usual in the O/S to be dealt with the same way...