Same grip size, but IMO the G4 has a better texture. The G3 has cheap and prevalent guide rods/springs for full power ammo, the G4's coax recoil spring can handle really warm ammo as-is, but can get a bit over-run with nuclear hot 10mm. I have a 3rd gen SF and love it, run a 21# spring, and it does well from 450-700fpe. Have fired a couple 4th gens though, they handle the same spectrum well enough, just get a bit snappier than mine once you get around 700fpe or above. If I were to do it again, would definitely go with the 4th gen.