I love S&W's as much as the next guy and have a safe full of S&W's (like most here) to back up those words. However when I wanted a subcompact plastic gun to make my 3913 and 6906 jealous, I couldn't decide between the XD subcompact .40 or the M&Pc .40.... so I bought them both (Buds has great prices).
I took them out of the boxes and headed for the range. Had some Winchester Ranger, Speer Gold Dot and Hornady XTP to try out. Also took some reloads that had some tight chambering problems in another gun. Most was 155 & 165gr but also took some 180 gr Blazer.
At 10 yds offhand hold, I was impressed with the M&P, it kept all shots in a 1 3/4"" bullseye circle. However what blew me away was the XD - all shots in one ragged hole! Not just once either, but consistently with multiple loads I put thru it ( neither like 180 gr loads)
I like the look and feel of the M&P and I like the smoothness of the trigger but my XD seems consistently more accurate with various ammo at all realistic ranges. The M&P did chamber & fire all of the faulty reloads that needed a slap on the back of the slide in the other gun. The XD fired most of them but did have a slightly tighter chamber and needed a couple slaps to seat a few. Since breaking it in I haven't had any ammo that didn't chamber in the XD, but out of the box, the M&P was more reliable with known faulty ammo.
I like the XD's visual chamber loaded indicator - not just at night when you can feel it (try looking down the little hole on the M&P in the dark, or even low light) but anytime I pick up the gun. Although everyone should treat all guns as loaded, I keep several around that are, and I can never tell if the M&P has one in the tube today... if I ever had to grab one I would look at the XD first.
I also like the XD's extra grip safety and ambi mag release (what's with the take-it-apart to reverse it nonsense S&W?). Carrying CCW, there are times I think the M&P is more comfortable in my waist and at other times I don't see any difference. The grip on the XD can protrude more in some carry modes, if your not careful. The factory mags are cheaper for the XD.
Although I like many things about my M&P I think the XD has better overall features and is, in my case, the better all around CCW defense weapon. OK, after looking at these old photos i guess either one would do in a pinch.