Thank you for the feedback - will definitely avoid the LUS A321 at all costs - sounds like a pretty awful way to cross the country.

You are making the 757 sound OK so maybe I will give it a try. There is also the possibility that I could fly DUB-LHR and then take a BA 747 LHR-JFK but that would mean I would need to get a hotel in Dublin for one night (because I am positioning from LHR). So it's just a case of deciding if the upper deck of a 747 is worth me paying for and spending an additional night in a hotel.

Thank you for your help and enabling me to at least eliminate the PHL (or CLT) options.