Well this is just my opinion. I drove the older Mule 550 for a number of years. It seriously lacked power. So when Kawasaki announced the Mule 600/610 with a bigger motor, same size vehicle I was stoked. Then I test drove one and was disappointed. They have a number of things going for them, but in my opinion, and this is after putting time off road at my property in the hill country and in W. Texas on a 4WD TransMule, is that even the bigger one is underpowered unless operated in Low range. Now this is in hilly country, rocky and steep roads and hillsides. If it were me, I would spend the money for the bigger Mule if I was going to buy one, but unless you need that style utility vehicle, there are others with much more power and abilities off road. For nearly the same price as the little Mule is the Yamaha Rhino 450, which is what I purchased rather than the Mule 610. No comparison really between the two.
The Kawasaki Teryx is obviously more sporty and expensive, but has power to spare. Polaris has the large (too large for me) Ranger, and now the much smaller RZR. If you need to do much work, the lack of a real bed on the RZR will probably count it out.
Honda has a very ugly side by side vehicle, that frankly after looking at the write up, I never seriously considered. Bush Hog has 2 different side by sides that are very good vehilces, similar to the Mule's only with better suspension and looks, at least to me.
Cub Cadet has slow moving utility vehicles as well. I hope that helps a bit.
