M&P Triggers
Every M&P trigger I have tried was too heavy. The M&P trigger can be fixed with drop-in parts from APEX Tactical.
Maintenance is the major overlooked factor in choosing a gun.
The advantage; however, goes to Glock in the maintenance department. Spare spring kits are low priced. You can buy every part (except the frame) for a Glock and replace it yourself. Buy Ptooma Productions The Complete Glock Reference Guide. Tools are minimal and listed in the book. I keep a bunch of spare parts onhand and the cost was under $100.
Don't accessorize your Glock. Add a grip plug, buy a Glock 3.5# connector, and add night sights. If you hate the grip, texture it. Other than that, leave it alone. If you start accessorizing, you can affect reliability. Reduced reliability is fine for a range gun, but unacceptable for a self-defense pistol. Spend the money on spare parts and extra magazines.
If I were going to choose a gun based upon maintenance alone, I would consider only the 1911, Glock, and S&W revolver. Of those, I believe it's difficult to get the hammer and sear parts from S&W (but I'm not sure on that). I believe that 1911 parts are more common than Glock parts due to sheer volume. The difference is that the person doing the maintenance needs to know more about the 1911. Glock parts should drop in without modification.
Grip Angle "Problem"
The whole grip angle "problem" is silly. It really isn't an issue and is just something people like to complain about. They like to have something to blame for their poor shooting performance. (Nothing new there.) I see it all the time on the range. I like to "test" their "bad" Glock for them by shooting a small 10 round group quickly. I then show the person their actual shooting problem(s) and teach them proper shooting technique. Trigger control is the number one problem I see, closely followed by an incorrect grip.
Anyone who spends time behind the gun will learn how the weapon behaves during slow fire, rapid fire, double taps, "hearts-n-minds" and so on. How do I know? It's not great for me, yet I have no trouble with the grip after 10's of thousands of rounds through various Glocks! The 1911 grip angle is about perfect in terms of natural point for my hand. Yet I have learned how to shoot Glocks accurately in all situations (point shooting, sighted fire, slow fire, etc). I line up the sights with the target and my eye and fire. My body overcomes any grip angle "problems" because I have trained with many makes and models of handguns. In rapid fire, I correct as I would with any other firearm. Don't waste your time thinking about "grip angle" for any gun--go shooting instead!
Between the two, I recommend Glock. I think the M&P may shoot a bit softer, but I see no reason to improve by 5% for 9x19mm. The recoil is easy to manage in both guns. If you absolutely end up hating the Glock, you can easily sell it...especially if it is a Glock 19!