I think the Glk. Other's triggers are more forward, like DA Revs. I also have small hands and I had to get the grip reduced on all my Glks.
MP has 3 backstraps, but the new Gen4 Glks have 1/2 now. Beretta
very large grip, CZ OK. Sig 226 fits me fine with short trigger. Go to a gunshow/dealer and handle them and if possible shoot them. Good Luck
Of those I'm pretty sure the Glock has the shortest reach. Kind of hard to tell which one will work best without actually holding it though.
About the M&P: the trigger reach is about average, but the small backstrap should help. The M&P does have a long trigger pull though. The trigger breaks just before it hits the stop on the frame.