all depends on your riding style, if you like to boondock and play in the trees stick with the 800.; if you are a point and shoot kind of guy that like to go up all day go with the 1100. just my opinion.
I've ridden both, and have the M1100T in my stable. Is the 800 lighter? Yes. Is the 1100 workable in the trees? Yes, it is. I've found the 1100 rides "lighter" then the M8 or M1000 two stokes we owned previously. I can take it anywhere I've ridden my wife's PRO RMK, but it does require a bit more body english, and throttle control then the two strokes. If you are not in good shape, the 1100 will ride you, not the other way around...
In 12's the 1100 t is a very very different ride. Mostly due to the steering orientation. I know you can change it and I believe the 13s have a verticals steering option...
The 800 I have requires more of a stand up steer hard ride style... Where as when I got on my buddies 1100t, it steers very different and you can just sit down and steer/lean. That being said it really all depends on your gut feeling. I had the turbo preordered but changed to the 800 and don't regret it one bit except loosing out on the extra 30 feet or so on high mark.
If you do but either I highly recommend dropping the front of the skid 3/4" in the front (thanks to kalebtimberlake for that) and ski change, also 38" front end to help with the downhill turns.
Those 2 mods are stock now on the 13's so you know it works. (Except skis of course)
My buddy has both the 1100 turbo and 800. Both are 2013 hi country limiteds and he prefers the 1100 turbo because of the power. I have ridden it myself and in areas where you use throttle the weight isn't obvious, only in situations where you are using little to no throttle you can notice the extra weight.
Being the owner of an 800 I have no shame in admitting how nicely the 1100 turns and climbs. It is front heavy in deep deep snow, both sleds I rode were 12's and M models though.