I'd have to vote for the XD, especially if your gonna use it as a carry weapon.
I personally don't own a M&P 9mm, but my friend that I always shoot with does. I own the XD service. We usually go to the range together and we go head to head on his dueling tree.
I cannot speak for how well he cleans and maintains he guns, but I know I'll clean mine about every 1000 rounds or every other range trip whichever comes first. With that said I'm on my first sleeve of spp in my tenth brick. That means that I have fired at least 8000 rounds of hand loads, and I know a case of blazer brass over the course of the last 15 months. Most shots were in rapid succession on the dueling tree without a single malfunction. I can think of three times my friends M&P malfunctioned one failure to eject and two failure to feeds.
Now given the shot counts when he had his issues I definitely wouldn't call the M&P an unreliable gun, I would just have to say that MY XD with MY hand loads is more reliable then HIS M&P with FACTORY ammo. (Big surprise, right
)
My reason for choosing the XD comes down to the features and feel for me. I love having the grip safety, it just gives me piece of mind when I carry. Though it can be a pain unloading the chambered round. (the grip safety must be compressed to rack the slide) and the XD just points better for me.
To me the most important thing in a defensive handgun is how it naturally points in YOUR HANDS. Handle the gun pick a spot (safely) close your eyes and bring the gun up. Then open you shooting eye (without adjusting the gun) and see how the sights line up. If they both line up for you then go with whichever one has what you want.