Polaris for the last twenty years. Ski-Doo before that. When it comes time to upgrade (soon), I'll give the new XCR and the new Doo 850 a good look.
As far as racing goes, I was under the impression that Polaris does extremely well in hill climbs and ovals . . . and gets a bunch of podium finishes and a handful of victories in sno-X every year. No mortal man is ever going to beat Tucker on a regular basis.