BA via Heathrow does have a lot to recommend it, including excellent lounge facilities at both JFK (less so Newark) and LHR, but you'd need to change terminals for the DUB flight. However, worth considering on an overnight flight because of the fully flat bed. You could, of course, also do a couple of days in London before flying on to Ireland as well.

You might want to look at the BA flight to London City Airport. This is a 32-seat plane, 100% business class, better food than the Heathrow flights and with plenty of options for a very quick connection (same terminal) to Dublin.

For a day flight (possibly the return) then a flat bed is less important so take a direct flight.