I see all this talk about HP or lack of, I'm here to tell youHP and speed are not what it's all about. It's about what will work for your situation and you enjoy it. I have a 2007 Rhino 450 and love it. I use it on mountain trails, mud bogs and also to pull trees on my place and it has all the power needed to get the job done. When I cut trees the logs are usually 18 - 20 inches across and usually 10 - 12 ft in length, the 450 hanles them with ease. I bought mine use for $4000 2 years ago. If you look you can find good use machines. The Mule is a nice machine if it works for you go for it.

 

A 325cc in a 1,100lb SXS may work but you have to admit it is pushing the limit.
I guess if its geared low enough a 8hp Briggs and Stratton will get it moving as well but its still not the best choice.