Letting the public decide will get very confusing... if you're gonnna do it round robin style... you choose the cars yourself. That's what was getting you flamed in the last thread the overall generality of your car challenge. There are so many Imprezas, Skylines, Lancers, Mustangs, Goats to choose from, it's hard to compare. like my last post in the Impreza vs Mustang thread, i don't know if you're asking me to vote for a 1996 Impreza Wagun or a 1969 Shelby Mustang GT500.. which would seem a little one sided. Here's a suggestion:
Take 4 cars of the Same price range, class and wieght, THEN ask people to vote (I.E. Accord Euro R, Opel Vectra 3.2 V6, VW Bora 4Motion 24v and Mazda 6) people might give you an easier time. Like you said, face off two at a time then, the final two go head to head