A couple months ago at a club meeting it was wet wet in the morning so i went to rubbers and i was the only one putting in whole laps, however when it started to dry out the car became very twitchy and hard to drive. Foams are much quicker in the wet.
My experiences are foams will slide but still have some form of traction, however if you slide enough with rubber tyres they will get to a certain point and just let go cause your car to spin.