Always holding one side of the grip isn't a superstition. It's about consistency. Even if a handle was perfectly symmetrical a wrapped base grip and overgrip is going to give a different feel to either side. Always holding one side just makes sense.
Babolat Pure Drive "Black" (1/4) w/ Kinomy Leather and Tourna grip XL and Luxilon 4G 16 @ 50lbs.