The problem with these sorts of threads is that it is easy to fall into the insider trap; the common conception is that so and so is great, but I know better because I know what I am talking about, be impressed by my discernment which distinguishes me from a musical lemming.
The thing to remember is that Joshua Bell and Yo Yo Ma are both very very good. Whether they are the best is debatable, of course, but still. They are both highly successful, and for good reason.
I'm not fond of Joshua Bell's body movements myself; I saw him performing the Four Seasons, and he had a predilection for stamping his left foot while seated, and spinning around jerkily while standing, which is a little startling. However, some people really like him. I love listening to his stuff. And he's certainly more experienced and successful than I am.
Also, it depends on the piece. A violinist that I know moves a little much, and it does detract from his sound; he isn't Curtis material, but he might be with less work on presentation and more on sound.
Watching him play Kreisler's Liebesfreud, for example, gave me a new enjoyment of the piece; I've always found it charming, but watching him bend his knees, lean back and raise his eyebrows, undulate his shoulders and in all ways deliberately overact in the cheesiest manner possible elicited an audible laugh at the end of the piece, from me and the rest of the audience - it's a humorous piece, and I can't listen to it anymore without chuckling. Did it detract from the sound? Perhaps a little. I didn't do my usual routine of closing my eyes every once in a while to see if he matches. But that is fine, it accomplished what he wanted to say.