I have extensively fired both the Springfield XD .40 cal and the Glock 21 in a tactical training class with Scott Warren as the instructor. The XD has a true single action that breaks and resets close to a 4# 1911 trigger. The Glock 21 breaks at close to 5# but has a longer reset and is closer to a double action feel, although shorter than some conventional DAOs. Both perform about the same as far as reset, recovery, speed is concerned. Accuracy was about the same.