I had the exact opposite experience with the M&P .45 today. It was dead nuts on and shot about as well as my sight picture. I shot the M&P .40 in a vertical string to the right of my POA. Part of that was learning the M&P trigger and the M&P .40 came before the .45.
Comparing the M&P to the performance center 1911 is really not a fair comparison. It would be better to compare a Burwell tuned M&P in an action shooting situation to the PC 1911, that is where the light weight frame and more than adequate trigger will shine over a heavy weight all steel gun. If you aren't making transitions than the M&P doesn't have much to offer you that a 1911 can't do better. The M&P is just another DAO duty gun, not a panacea. I like to think of it as the poor man's mass legal 2011 with affordable mags.
There is also weight for carry but that isn't a factor with my restricted license.
The front sight dot (especially fiber optic) is pretty essential for action shooting. Black sights shine for precision paper punching but not for close shots at 7 yards on IPSC sized targets. Different tools for different schools so to speak. The black is always there for those 25 yard shots.