Which pistol should I purchase, semi-automatic shotgun?

I own the Glock 23 and an M&P .40. My vote is the M&P all day long. Better grip angle WAY more comfortable in the hand, adjustable back straps (Gen4 Glocks have that option too). I can't say enough good about the M&P's. Although I've shot an XD45 which was very comfortable in the hand it a very different feel than .40 so it may not be a good comparison. BUT both M&P and XD will most likely feel better in the hand than the Glock. M&P are pushing out Glocks in PD's country wide which is why the prices on them have come down. I'd personally go M&P.