Own both an M and an XP. Will say that I like the XP better for handling and power but have had many, many issues with it. Blown motors, clutches, etc.... The M has been completely trouble free. runs like a top every time. Really thinking about getting another and dumping this XP.
I have a friend who's in the same boat....His XP ripps! (when it works....)
He's looking at getting another M. He had an '08 M8, then got the XP, and has kicked himself for it eversince. He'll admit that the XP is better than his M8, but there is something to be said for "Turn Key" reliability. And so far, doo has yet to give him that. I'll give him till Arctic Man up here in AK till he is back on a Cat.