I just have a little Honda Rancher 350cc. I love it. It wasn't too badly prices and gets me anywhere around here I need to go. I have plenty of room to bungi on my climber. It is not too bulky and can get into some tight areas and doesn't weigh too much either. I have had great success in getting deer & bear out of the woods with it.
I would love to get one of the big quads (Grizzly 660 or Brute Force), but it is just overkill for what I use it for.
Honda makes an excellent quad.
My brother in law has a Yamaha Big Bear 400cc. Nice machine too... just a little louder.