I never really liked 2D bone animation. It would look smooth, but it wouldn't really be good animation.
But it's not like we're going to have a character as well-animated as SOTN Alucard again so.
That's the thing, you can actually combine the 2... Hell lot of work though. What I mean is have states for each body part. The big problem with bone animation is that, when you see them, it's only one picture being rotated on an axis, but... imagine if each bone had like 7 different states.
Example would be the body facing left, and a state for each turn animation as he turns right. (7 is just an arbitrary number I came up with) but it would be hard to implement. I don't think I've ever really seen this implemented though. Closest thing I know of is just 2 characters with the same bone animation, but one state is one character and the other being the other character. Ryu and Ken would work, since they have pretty much the same moves.