LBJ has a much better handle and is capable of playing point guard full time. Although Bird was probably an equal to LBJ when it came to passing and vision, Bird did not have the handle.
LBJ can also defend any position on the floor, including PG. Bird was capable of guarding 3, 4, and 5's and a lot of 2's, but he wasn't going to guard the PG.
Every other part of their game was pretty similar, though Bird was a better shooter and probably a better rebounder. However, based on LBJ's versatility, I got to put him ahead of Bird.