Depends on what you're looking for. I can't speak for Jebs, but I shot a .555 and a.575 yesterday with Federal TSS 9's, and to me something in between would be perfect. The .555 was softball size at 20 but killer at 40. The 575 was much more forgiving at 20, but half as good at 40.
I'm personally going to likely pick up a.565 or .570, I think either would be a happy medium