I've been deadlifting with my right hand under the bar and my left hand over the bar without changing it up. I don't really do much other trap work (DB shrugs once in a while). My traps have pretty much exploded recently, but my left trap is alot bigger than the right. Anyone think it could be related to using the same grip all the time? I'm a little weaker when I go the other way, so I don't really like to switch it up. Anyway, I guess I'll just pack on another 10 pounds of meat and no one will notice.
seriously, there shouldn't be a difference, but switch grips if you want, I can only get one wrist to rotate enough to grip under so I only do them 1 way and i have never noticed my traps growing at a different rate, you are probably just paranoid. Post a pic if you really think it is bigger