I always start in Galaxy City too, for all the reasons stated already. It is less crowded and the layout is better for non-travel powered heroes.
As for what feels more 'heroic' from a RP point on view? Sure Atlas Park might look more impressive, but given the hero population there, Galaxy City is in more need of protectors. So which is more heroic? Going to the place where most other heroes already are or the place where villians are less apt to be stopped by heroes? I say the latter.