I agree with kindaslow, the trail is really the determining factor here. You wouldn't believe the power your full suspension bike cost you on a climb. So consider if you spend more time climbing or speeding over rock gardens and bombing downhills.
Most of the fast guys I ride with are on front suspension only, mostly due to the energy efficiency lost to rear suspension compression on hard pedal strokes.
IMHO, front suspension is good for bike control when taking a serious hit, but your legs are good enough for rear suspension and the benefits outweigh any comfort gains.