So, I've owned a Glock 23 (40 cal) for a few years now. I haven't owned any other guns, so I never regularly shot any other handguns until a couple a months ago when a buddy of mine (who owns a ****-load of guns) let me shoot some of his. When I say "let me shoot," I don't mean a magazine, I mean, we were shooting for several hours.
The main gun I used was a .45 1911, and what I noticed is, even with the extra power, I was still a better shot with it than my own glock. I could only guess that this was due to the aggressive grip angle on the glock.
So I did what any idiot would do, I purchased a .40 S&W M&P. After a day of shooting, here is my comparison of the two:
Looks: Totally subjective, I know, but I like the looks of the glock more. The swirl pattern on the m&p makes it look a little like a toy, although, it looks better in person than the pictures I had seen.
Slide: I like the slide of the m&p more, the fish scales are easy to grip to rack the slide.
Field Stripping: The field stripping is no contest, the glock butt-rapes the m&p in this category. To take the glock apart, you simply push down on the lever on the side, and a small pull on the slide backwards removes the slide off. The m&p on the other hand, there is a pin on the inside of the gun that has to be pushed down, and if that pin isn't in the correct place when you put the slide back on, game over. Assembling the gun again is also easier with the glock, the slide simply slides right back on. Assembling the m&p is a bit clumsy, because you have to work the switch on the side. Also, the m&p comes with a tool located in the grip that's all but worthless if you're in the field. I had to pry this thing out with a butter knife (and even then, I was concerned about the butter knife holding up). Thanks, but I'll just reach for the nearest ballpoint pin. Also, the spring in the m&p was showing rust o_O
Feel in the hand: Even after putting on the appropriate backstrap for the m&p (which comes with three, for various-sized hands), the glock still felt better in my hand. Subjective, I know, but thought I would throw it in.
Actual shooting: Using the same ammo and shooting back-to-back, I can say that I felt more kickback in the glock. Shooting the m&p felt closer to shooting a 9 than shooting a 40. Not sure I necessarily liked the trigger in the m&p, but it didn't bug me like I thought it would.
Performance: Well, here is where the rubber meets the road, all the other stuff is minor BS when compared to the actual performance of the weapons. After all, we buy guns to shoot and be the best shot possible, right?
That being said, I'm a much better shot with the m&p, even though I was much more familiar with the glock, already having put a couple thousand rounds through it. The pictures below are of my last target of the day. The first one is with the glock. I colored them orange to be easier to see, and you can see a couple outliers, one in the shoulder, and one in the traps area. The grouping is "okay," but not awesome. Compared with the m&p, no outliers, and a great grouping. I guess the shots speak for themselves, I may be dropping by the nearest gun shop to see if they're interested in buying a glock
Edit: I removed how far away the target was, because I didn't need a derail of how much better of a shot anyone supposedly is than me with their particular gun. That's not the point. I'll just say that it was a good distance away; further away than you would be shooting anyone in a real-life scenario.