I Test ATVs and side by sides for a living (snowmobiles in the winter) I have a Can Am Commander XT 1000 here right now AND we just got our Polaris RZR XP 900... the RZR is the absolute most awesome vehicle Ive ever driven. It will do 80mph flat out, I can clear 40-50 foot table tops and double with it... its just an insane vehicle, but its SO smooth. Both in how it rides and in the power deliver. The Commander is almost as fast but the suspension is very stiff... not nearly as plush as the RZR... the power is also very hard to modulate smoothly. It certainly has TONS of power... but its just not as controllable as the RZR.
If it were my money and I wanted a vehicle to have FUN with... id go RZR... if I needed to do more work AND have SOME fun... id go commander.