Originally Posted by Mountain10mm
Besides the interchangeable grip on the Gen 4, what else changed from the G20 SF? Does the Gen 4 have the newer compound recoil spring? The bigger magazine release button?
The Gen4 G20 has a dual recoil spring for the first time in the G20, and the more aggressive Gen4 grip texture, larger mag release (reversible) and the backstrap adapters. With no backstrap adapter installed, the G20 Gen4 grip has essentially the same dimensions as the Gen3 G20SF. Others have reported that the Gen4 G20 "feels" smaller than the G20SF in the hand, likely due to the uniform grip texture around the entire circumference of the grip.
Below is a good video review by GT member plouffedaddy
and his related GT thread: http://glocktalk.com/forums/showthread.php?t=1427691