Given the choice I would go with Aidan as, to me, it's a proper name but then again I live in Ireland where it's a solid, no nonsense name like I imagine John or James would be in the UK.
Threads like this make me smile. I read one where posters were having convulsions in horror at "Kevin" being the worst of all names. If you look at where the name is actually from it's completely unremarkable, albeit an English spelling of an Irish word, just like Aidan.