If you're looking for something that's all-terrain that you can rough up and work it hard on your farm, then I'd go with Polaris. If you want something fast, then Can Am might be the better fit.
I just switched from Artic Cats (we've had 3 that have all had lots of repairs) to Can-am. Spent $1,700 to extend the warranty to 6 years! Seems much better built and does not have wrap around dust issue like the Artic Cats.