Nash has MUCH better court vision & outside shooting, Kidd is still the best rebounding, all around PG of the league, but i don't hold any other PG higher than Tony outside those two mentioned players. I use to put Billups on a higher note, but this year he has fallen a bit up to this point.
So, the 2nd tier PG list should go with these guys : B Davis, Tony Parker, Deron Williams, Chris Paul, Chauncey Billups, and their exact rank is pretty darn arguable, no clear cut conclusion outside homerish or trollish opinion.