I, in turn, would rank Jason Kidd and Steve Nash 1A and 1B, respectively.
There's really no point arguing who the better one is because both are excellent point guards. Bottom line.
The reality is, both have different strengths in their game. Jason Kidd, for all his brilliance, cant shoot on a consistent basis, hence the nickname "Ason Kidd". For his part, Nash is one of the best shooters in the league. If memory serves me correct, he and Dirk Nowitzki are the only two players to eclipse the 50-40-90 shooting percentages (FG, 3pt, FT)
While Nash is a great shooter, he has never been known to be a great rebounder and defender. Jason Kidd? A triple-double machine and a great defender in his own right.
So really, I see no reason why you dont pick Jason Kidd over Steve Nash and vice versa.
Both guys are awesome and when it comes down to it, both are winners.