definitely agree with the 700 for trail/dunes. cant go wrong with the fuel injection, even though i believe the brand new yfz are fuel injected those are still not gunna have the low end, luggable power that the raptor has. yfz will respond better with mods but with 700 cc's you dont need to do much in the power department. especially if its gunna be ridden easy an not revved to the moon like most 450s. get some nerfbars, adjust the suspension an shed be set to go.

 

The 450 are the motors used in the 450 Motocross bikes so they will need a rebuild much sooner than any other ATV out there. You do not get 45hp plus out of a 450cc four stroke without stressing the motor to its limits.

The 700 can also makes 45 hp and more torque but it can be more laid back and lazy about doing it.

 

top speeds are close on all the fast quads probably because of the manufacturer agreement that they set at 75-77. i had a predator, a 450r, yfz etc and they were all about the same on top. i never rode a 700, but its made for trails and a bigger engine ALWAYS has more torque.