The whole "Governor's make better Presidents" argument is kind of hamstrung by the fact that Obama was the first Senator to be elected President since JFK. The sample size of Senators turned President to date is exactly two men in 56 years, and one of them only served one half of one term.
I would call it inconclusive. For whatever it's worth (not much), Obama has been a better President objectively than either of the Governor's who proceeded him.
I'm not sure how Obama is
objectively better than Clinton.