If for whatever reason that trip gets cancelled, DUB becomes more advantageous. There is a program to have your Global Entry interview on arrival in the US, no prior appointment needed (if conditionally approved), and DUB preclearance participates. It often involves some waiting around for an officer to become free. I imagine at DUB the wait won't be too long and the officers will be good about making sure you are out in time for your connecting flight, so this is an efficient way to use up the surplus connecting time other have mentioned.