Flying to NYC from DUB you can clear US immigration before you leave Ireland making arrival much less stressful and you pay a lot less government tax. You have the choice of EI, DL and CO. DL and CO were barred from LHR because of the agreement between the UK and US government, that has been swepped away now by a new EU agreement. DL are meant to be commencing services from there in '08 to ATL and JFK I believe.