I'll try not bash one or the other. I have ridden Doo for 14 years or so, Started on a 1999 670 Summit X, 136" track, old style sled. I had 5000 miles on it when I sold it about 3 years ago I never did anything to it nor did the guy before me 1200 miles when I got it.
I ride a 2004 Rev Summit X 800 144". My friends all ride newer Pro's two on 2012 800's and sister-n-law on a 2013 RMK 600. They have always been on Poo's, and they have always done more wrenching, pistons, crank replacement twice, this is on 2003 RMK's 800's, then they upgraded to the Pro's. One friend put the "piston kit" spacer and piston's in his 800 he only has like 1700 miles.
I have been looking for a Pro or RMK see a lot of them on Craigslist, but also notice many have had new motors "Warranty" replacement. Or work done. Maybe it's just Poo has more sleds out there or you hear more "stories" not sure I know Doo isn't without problems.
I really think both the Poo and Doo mountains sleds are very good whichever you pick. Each person going to fit one better than the other. For me I would choose the Ski Doo, just my .02.