I have a fairly extensive background both in the sport UTVs and the more utilitarian models as well (used to have an off-road racing shop, currently own a few UTVs, and work for another ranch that has ~20). My straight opinion is that Polaris has nickle and dimed their lineup into being the cheap and easy option. Lots of issues with machines right off the showroom floor (look up Polaris Stop-Ride announcements). Older machines suffer from some of the same issues, but there are a lot of aftermarket fixes out there.
If you're looking at Polaris, I'd stick to the full-size machines (not the Ranger 500/570) and try to get one with as few miles/hours as possible. Motors are good usually to ~5k miles, less if it's a dusty environment or maintenance was deferred/skipped. The General is a cross between a RZR and a Ranger, and may be worth looking for if you can find one in your price range. RZRs have small bed storage areas and you'll be seated lower to the ground than a Ranger or General.
Can Am has a similar lineup to Polaris, with their sport vehicles being a little more sport oriented (lack of storage). The Commander is the competitor to the General, and the Defender to the Ranger. Can Am drug their feet on updating the Commander lineup for a few years, and the previous generations have some frustrating design features. Their newest generation of vehicles is the best on the market currently in my opinion.
Honda has the Pioneer, and in my limited experience it's a good machine. I've also been around a few Kawasaki UTVs and the owners have been happy with them.
The biggest suggestion I have is to go over any machine with a fine tooth comb before purchase. Take a floor jack, raise the front and rear wheels off the ground and look for worn suspension bushings, loose wheel bearings, & sloppy tie rod ends and ball joints. Pull the air filter and see how dirty it is. Ask for any maintenance records/receipts from parts purchased.
Stay on top of preventative maintenance, replacing parts before they fail/take out other parts is of huge importance with these machines. They are easy to work on, and definitely worth having in the stable as a recreational & utility vehicle.