That's a tough call because I honestly like them all but to me it's the Styling of the Earlier A Bodies that is really appealing be it a Dart, Valiant or Barracuda. I really think the Earlier cars struck a better balance with their rounded fenders while still maintaining straight lines and the interiors still had at least a modicum of personality. The later Darts, Swingers, Valiants, etc. while I love them too are essentially just a box with four wheels.
Nowwwwww, when it comes to actually having to modify and work on this stuff on a stock chassis get me far away from the early stuff and put me in a Demon or Duster which also have great lines externally but suffer the downside of totally generic interiors.
This poll would have been Helluva Lot better if you could have voted for a particular year and model...