It depends on which position you play. For strikers and defenders it is extremely useful for it to be above 80, whereas for midfielders it is great to have it above 75, but mine is above 80 and I find it very useful.
Body balance is essential because your player won't get knocked down, or knocked off the ball as easily when dribbling. I also makes you better at tackling, or rather knocking other players off the ball. It is, bascially, your player's strength. For attackers it might help in the air as well, but not sure.