Gnil,
supersport RS is the race focused tire of the range - supersport r is the equivalent of sport maxx race 2.
supersport RS is an equivalent to the Michelin cup R but better ;-)
RS will be nice on track, but obviously with a race compound you will not expect miracles when wet. If I were you I would test the supersport R, and if you have spare wheels, a set of RS for track days.
rgds,
--
991.2 GT3 PDK Black on black