Re: 5.25" 1911?
An Open gun with a threaded bull barrel might count as a 5.5" 1911 in some technical sense.
The reason you're seeing the XD(m) 5.25 advertised is that they screwed the pooch by making it a 3.8" or 4.5". They should have offered a 4" and 5" (like they did with the XD) and are trying to make up for it.
When I got my M&P, I considered a Glock 34, XD 5", and the M&P Pro 5". At the time, you could get a brand new XD with four magazines for $420....it was a great deal. I should have bought both the XD and the M&P on account of only the price of the XD, but I ended up going with the M&P, and I'm confident I made the right choice.
The XD(m) was out from the beginning because of the 4.5" barrel. If the 5.25" XD(m) was offered then, I would have seriously considered it.
I still think the M&P has a lower bore axis, but the XD has a decent trigger, metal mags (just like the M&P) and interchangeable backstraps, so it's competitive.