Going to a glock from shooting 1911's and similar frames will be a step backwards in itself. Unless you want to relearn everything you know stick with something with a similar grip angle. The SD is a great weapon. The M&P's are a little larger and thicker unless you get a compact but even then it is minimally smaller 1/4" in length and about 1/8" shorter but still thicker. The trigger is just what I look for in a SD gun and the capacity is just right too. 16+1 in 9mm and 14+1 in .40.

Where are you located? If you are anywhere near you are welcome to come shoot my poly smiths. I own at least one of each.