Well as far as the original question goes and looking at their entire respective careers, I say it's Kidd. Kidd is the better all around player when you take defense into consideration, and his offensive numbers are better than Nash's and right there with KJ's as far as career ppg, apg, and he blows them both away in rpg. As fars as career totals, Kidd again blows away both guys in assists and rebounds, and his points are right there with KJ. Steals and blocks are not even worth comparing, Kidd is on a whole different level there.
Throw in the fact that he has made it to the Finals twice, albeit from the lesser conference, (well actually the West was the considered the lesser conf in '93 when KJ made it) and the co ROY, All NBA, all NBA defensive and Olympic honors and I think that pretty much seals it for J Kidd.
Now looking at them as Suns, I would think the nod would have to go to KJ just for longevity alone. Nash probably has had the best 2 (going on 3) year run of any pg in history let alone any Sun and has the MVPs to prove it, so Kidd finshes up behind both of them as far as what they did in a Suns uni. Interesting topic and opinions.