You should not add the +1's without the minuses as that can mess up the voting, I've seen it happen on one or two of these games on GTAForums. The change may seem small, but down the line it can have adverse effects. If people can't vote correctly, they should be ignored until they learn. Rules are rules, it would be like starting before the sticky (in the MCEC2), it might not matter, but it could.
This goes back to a long-running feud I've had between the two cars as far back as GTA III. I always prefered the Infernus while my friend liked the Cheetah. That, and I really don't like the look of the Cheetah in GTA V.