Deffinitly direct on a day flight
Advantages of immigration in DUB and not having to connect far out weigh any hard product benefits you'll receive.
That is is unless you're after the TPs and or are just a flying nerd and don't mind the connecting experience!
Id take an AA 77W but BA coming back for the sleeper service if you'd been doing J back.
Thats the other discussion needed for this thread, why not reverse the Y, J legs?