Depends.
A high ping will help you out when you're on the offensive, hurt you when you're being defensive. You see people where they were a short time ago, making it MUCH harder for them to avoid your gunfire.
A low ping is helpfull on the defensive, it will make sure that when you move, the person behind you sees it ASAP, creating as little lag there as possible. A high ping behind you though can negate it pretty well.
This comparison is based on ping only, assuming everything else is working well. If you have a bad ISP(SHAME ON YOU! get a real isp!) without a stable ping, things will be different.