The GT3 RS isn't really a fair comparison since its such a crude, stripped down racer. Both the GT2 and F430 however do have some degree of comfort and are also similar in base price (though dealer markup im sure is far more for the ferrari). Also, if you think about it, the GT3 was pretty much as quick as the 360 CS around a track, and we know that the GT2 is significantly faster than either car. Now, I beleive the F430 was only about 0.2 seconds faster than the CS on their test track, and many of the people that have driven both feel that the CS can achieve times equal to or slightly less than the F430. With that in mind, its hard to say which would really be quicker on a track, though I feel the GT2 might have a slight edge. That said, the GT2 is a very difficult car to drive at the limits, and so I'm sure the F430 would feel less unnerving to drive quickly around a track.
But the sparks are really gonna fly when the 997 TT comes out...