claede:
Not a bad choice

.... Personally (no arthritis), I find the M&P40FS and 40C to be quite comfortable, too, but I'm a 1911 guy, and the 40's only slightly different. Snappier.... OTOH, all of my 1911's are steel - nothing "lightweight". The M&P's are quite a bit lighter, which increases apparent recoil.
I have an M&P9C, 40FS, and 40C. My daughter (she's 28, but fairly petite) finds the 9C rather better for her use, but is happy as a clam with target reloads in a full sized 1911. She tends to shoot a little to the left, resulting in a suggestion that she tell the BG to move a bit, but since she won't carry it, hardly germane. She likes to make noise

....
My wife's got arthritis and diabetic neuropathy. I don't think she'd be able to handle anything but a 9mm or .22, but she won't come out to the range. "Not ladylike"....

She has shot .45's before, though, with excellent results, but that was before most of her problems surfaced quite a few years back.]
Enjoy the new M&P! I don't think you'll regret it.
Regards,