I just had the same dilemma. I ended up going for the 900 s I was tempted with the 2000s but they were slightly too exspensive for me.
Im pretty sure the 850 900 are extremely simular.
The buttons the jog wheel and the pitch are all the same.
There are some good comparison video s on YouTube.
I would link you but I'm writing this from my iPod and I CBa with the hassle