I ride a 14 XM with a "silber'ish" "boostit'ish" turbo kit with very good DJ and SHR clutch work. I run it at 7 psi and it is a handful and a lot of fun. I rode a 18 175 850 this last week. It works but powerwise it doesn't compare to my xm. Also I rode a axys a full day as well and it is snappy.
The 850 seemed to accept body language a little better than both the 800 and the axys. In my opinion I would say that was the major strength. the axys got better for me to work as I rode it more.
Long story short. I am not ready to give up my turbo 800 even it is a little harder to sidehill.
That's why they make Turbo kits for 850's :face-icon-small-dis