I started out with a first-year Ski-Doo Rev for winter 03-04. I HATED that sled (a long but separate story)... but where I'm going with this is the motor problems. Those 800's had ring delamination issues and were failing frequently. I know of one guy who had a long extended warranty and rode a LOT (he's here on SnoWest but I won't name him) and word has it he got two new motors a year the whole time he had the sled... one at midseason and one at the end of the season (or start of the next).
Then there's Polaris... remember how the 800 had crank issues where the primaries were snapping the end of the crank? The 700's seemed good, but the 800 was a problem.
Then there's Cat... I don't recall them ever really having motor problems. I've heard many stories of their motors (back when they were Suzukis) lasting thousands of miles without a top end job. I haven't really heard of problems since they switched to their own motors either.
Yamaha... I haven't paid much attention but I don't recall really hearing much about motor issues. But their motors also got used in motorcycles and other things so they got a LOT of use and testing and refinement. Look at the power you can get out of any of those 4-stokes with a turbo. Yikes. This was before they started selling rebranded Arctic Cats.
My point is that the two main players in the sport (Polaris and Doo) seem to have had some significant engine issues over the years. Even today, Polaris seems to have recall after recall. My '23 Khaos 850 has had two recalls... the last one was that one about having to use ethanol fuel because of some ridiculous 0.01% chance of a fire due to static buildup... yet Polaris has been known to deny warranty claims when they do fuel sample tests and discover ethanol. Seems pretty shady to me. And my new 2024 Sportsman 850 that I bought last March... less than two months later it got a stop-ride recall, something about a possible leak from the fuel pump. They didn't have a fix until SEPTEMBER. That's absolutely unacceptable.
All in all, Cat seems to be a pretty reliable brand.