AWD is used only by Polaris and Can-AM. The difference being while in 4wd the ATV is still in 2wd unless the rear wheels slip then the front wheel engage until the rear regains tractions then it returns to 2wd for easy steering.
Also AWD is true 4wd like diff lock where regular ATV 4wd is really 3wd because the ATV only sends power to one front wheel at a time unless the ATV has a diff lock option.

The rear wheel slip to is so sight and quick on AWD that its impossible to notice or feel .Here is a good video to show how instant the AWD system works.,

Its not about that, but why look at a 650 with no power steering that cost more then a 850 with power steering.
You can make a fast machine go as slow as you want but you can,t make a slow machine go as fast as you want.