I don't have an M&P40, but when asking this question about any pistol, it's best to specify the approximate range to the target.
FWIW I've found that inside 10yds, the difference in POI between different bullets weights in a larger-caliber pistol often isn't readily apparent, at least when using full-power commercial ammo. Unless the shooter is unusually skilled, his or her hold will usually cause enough variation between shots that the difference in POI caused by the ammo isn't readily apparent; for instance, it's difficult to differentiate a 2" group from another that's only 1/4" lower.
"Smokey, this is not 'Nam. This is bowling. There are rules... MARK IT ZERO!!" - Walter Sobchak