I've only flown transatlantic a few times but the American carriers have always let me down - poor service, overbooked flights, rude staff, etc. Aer Lingus are much better but, at least the last time I flew with them, their in flight entertainment was awful. I'd happily fly through London and waste the extra two hours than suffer an American carrier out of Dublin again.
Pre-clearance is great if you're transiting though an American airport though, it really eases the pressure.