I think the best dune quad out there is the KFX 700, I had 2 sold one and still have one that I kept for when I don't want to use the Rhino.
I have had tuned Raptors, Banshee, 250r, and have ridden most others and I still prefer the KFX. I can stop at the bottom of a hill then when I decide to go just hit the throttle and go up and over most anything and on the way down the other side the engine brake works great. Hills that I had trouble going over with the other quads was no problem with the KFX and I use to get stuck alot with those, I have yet to get stuck with the KFX.
Now the clutch boys will not agree!