i only buy gen 4's. i like the grip better.
but i have to say, if you can find a rtf2 gen 3.5 get it. that is the best glock ive tried. the grip shape feels diferent than my gen 4 with and without 1 backstrap, and the rtf is amazing. some complain its too grippy, but i dont find that.
i may grab one for ipsc shooting.