Well I say reality manipulation but I meant he can just turn inanimate objects into reality, which I suppose is a kind of reality manipulation. I can't remember much of Stein's speed feats tbh but Kabuto is so damn powerful now days. I assume it would be fair to say that he is as fast as or faster than Sage Naruto who was pretty damn fast and dominated Nagato for a while. I think in terms of surprise attacks Kabuto wins and in this battle I think surprise attacks are just what one of these guys needs in order to win.
In terms of attack, Stein has some powerful attacks but when they hit they will probably just end up hitting a snake clone.