The worst in terms of competitiveness are Anita & Arthur (13) and Debra & Steve (4) - lovable people, I have no doubt, but they belong on the race as much as I do on American Idol. Teams like those are simply unfit for the grind of the race, IMO. Horrible casting.
Nigh impossible to say who were the "best", we saw so little of them. I go for Dennis & Erika (5) on potential alone - fit, got along well, seemed pretty smart, eliminated because they gave up a cab to another team, if I remember correctly.