No one knows. Based on his limited experience at Ohio State, his performance at their Spring game, his size and his arm I would say at this point better than all of them but Mett.
Mett had a true NFL arm, but had zero mobility. Burrow might end up being better than all of them. He will have a better defense than Mett did and that helps. I think he can take LSU from a 7 or 8 win team to a 9 or 10win team. Given LSUs brutal schedule this year, winning 10 games would be quite an accomplishment.