All three serve the same purpose and are about equal in quality and accuracy. Personally, I'd go with the M&P (again). I wasn't a fan of the way the XD shot and absolutely hated the grip on the Glock. The M&P shoots just fine for me in IDPA and I can conceal it reasonably well.
This is really a rehashed question, you know. The general consensus every time it comes up is to rent or borrow all three, at the same time if possible, and see which one you like best, because it is all up to personal preference. Some swear by Glock, others by XD, and some by M&P. Then there's the people that chime in telling you to skip the tupperware and get yourself a 1911.
We can give you pointers, opinions, and experience stories, but you'll only be happy after YOU do the research and select one yourself.