I have extensive miles on Can-Am, Polaris, John Deere, and Yamaha UTV’s. Most comfortable would be Can-Am or Polaris. Most heavy duty would me John Deere (but if/when it breaks, be prepared). Yamaha is a good mix of comfort and reliability. I will not be purchasing another Polaris machine in my lifetime, too many problems with the ones I’ve owned and too many known issues to deal with. They look and feel like awesome machines but the reliability is spotty at best.
If you are looking for a UTV that can be used on the trails and for work, I would hands down check out the Can-Am commander. Rotax motors are proven and the whole machine is awesome. I owned a Can-Am Maverick briefly to get the wife into the trail riding sport and we both loved it, she just wanted handlebars instead. BRP machines were known for years as the rich mans machine, but that is no longer the case. Price out an equally equipped Polaris or Yamaha and you will see. Also check out how well BRP machines hold their value…
I have no experience in the 4-seater Yamaha Vikings but the older 2-seater Rhinos are awesome machines. One UTV brand that isn’t as well known is the Kawasaki’s. The Mule and Teryx have proven themselves from all the reviews I have seen, I just have not been in one.