It's a little like comparing apples to apple sauce.
It's only natural to compare the M&P to the Glock. They are both black, polymer frame, striker fired, steel slide and same type of safeties. However, they are very different guns.
While they both use a trigger with a built in safety and a trigger bar, that's where the trigger mechanism similarity ends. Even though they both have polymer frames, they are wildly different. The M&P was designed from the ground up with ergonomics in mind. The Glock obviously was not.
So, even if there was an M&P with exactly the dimensions of a Glock, it would be a completely different gun and they still wouldn't compare well. The dimensional differences are so small, one is not more concealable than the other.
While I believe I understand the reasoning behind the OP, it's really a moot point.
