Kidd over Nash because his offense is better than Nash's defense.
And sure, defense matters least at that position but you can see that its pretty much impossible to win a ring with weak point-of-attack defense. Kidd could guard 1-3 while Nash was a liability at every spot defensively.
And while sure, those Nets teams weren't very good and played in the weakest conference of my lifetime, Nash played with an amazing roster of players during his time in Phoneix. Marion, Joe Cool, Amare, Diaw, etc
Also, end of the day you saw it down the stretch of their careers. Kidd got a ring at the end as a starter cause he maintained his defensive value late into his career.