Re: those who are sledders....
I ride Polaris as well. To answer your question, it now depends on what you want to spend. If you have the money to buy new, I would definetly suggest the new Edge machines from Polaris. Every one is raving about them all around. If you're buying used, triples are a bit better on fuel in the long run, they make their power with less effort. Stay away from machines with pipes and clutch kits, you don't want to buy what someones already screwed up. I just spent this summer fixing the previous owners "upgrades" on my 96.
all four makes, put out good machines, of course most guys are very brand specific and will tell you theirs are the best.
I'd probably do A Ski-doo or Polaris for the ditches, just because these guys have their suspensions ready to go and easily adjustable.