I think it all depends on how hard the fucking is. If you are fucking nice and slow and not using plunging, deep thrusts, I would say the uncut cock would have less of an impact on the cooter than the cut one.
If you are fucking like wild javelinas in the Arizona desert heat, then I would say it doesn't really matter. Eventually the pussy is going to dry out anyways... at which point you either:
A) Grab the K-Y
or
B) Put it down her throat
