I vote for A/C. Two reasons are: 1. Defogging the inside of the windows. I hate having to do that with a squeegee while driving. 2. Resale value. You may have to sell the car someday, God forbid! and that will be a good selling point.
Of course, if it helps get you some action with the ladies, all other reasons become unimportant.
I vote for Vintage Air. Jack Chisenhall is a hot rodder at heart.