Just go with the Can Am if you want to take riding seriously. I've taken mine more places than most people ever dream of without one hiccup, except for the hump to shift
You are going to get every opinion under the sun. Do some research on ATV forums (which will likely take you to Can Am).
Im taking my 800 Outty xt on a 3 week hiking/mountaineering trek this summer, and shes been out for a long time plenty before, rides hard, smooth, and without the need for maintenance that goes into popos or kittycats. In this case you really do get what you pay for, look at the DAKAR 2013 for PROOF!! All Can ams, most pros ride them. They are the best.
The Yamaha Grizzly would be my second choice, but ask anybody unbiased and in the know - Can Am. And also, for hunting purposes (not steep technical riding) , I might even just go with the 650 xt outty save some money, some gas, some weight, etc.
Source: A lifetime of riding with all different companies.
CS
EDIT: If you're also looking at tires I would recommend the Maxxis Bighorn 2.0 or Kenda Bearclaws. Just switched my old ontario mud executioners to BC rock crawlers and it made a world of difference.