You should check out the reliable factor . I bought a 2014 xm and it is in for warranty all of march [ the best time to ride] clutch and stator wtf very displeased.
I have a '13 xm 163" and upgraded the shocks to raptor shocks and beefed up the rails with the stiffeners. I pound the crap outa it on the trails up and down the mountain. With 6+ years son x experience i look forward to the race down to the trailers. Now with the new shocks its almost the same price as a free ride. Plus i got a wrap to make it look just as snazzy as a free ride. You really can't go wrong either way but will have to put new shocks on a summit x.
I have a 2013 Freeride 154 and what I did was got a 35.7-37" front end and got my clicker shocks shortened/revalved. I have it on 37" wide and it handles like a summit (a little heavier but it's not that noticeable) and has the good suspension and strength of a Freeride. In my opinion it's the best of both worlds.
I have a 14 freeride and a 13 summit x both 154. For me the freeride is my preferred sled, I run it on the narrow front vs wide on the summit. The biggest downfall I found is the wide boards, when riding crappy snow with a thick crust over soft snow they definitely do get hung up easier than with the summit. The last thing I did to the freeride was add an aerocharger, seeing as the tunnels are the same width from the rear bracket back I don't notice any more dragging board issues