I don't know how we can really argue this without going into performance and handling aspects. The exterior and interior styling is extremely subjective and you can't argue someone into liking it.
I know we know who the winner is in terms of performance but I think in this case you either like the Mustang styling and want it more then you want the higher performance of the Camaro. Nothing wrong with that at all. I think both cars are REALLY good looking cars and I'd take either one gladly, but for pure performance I'd pick the SS.