Yikes! I really should make and effort to visit the fforwm more often!
My belated opinion having done both
NYC Heathrow Manchester (then trains)
-and-
Dublin Cardiff
is DEFINITELY Dublin Cardiff!
As @joanalciati says Dublin is calm & cleanâeasy peasy. and the Cardiff airport is small so itâs nice and calm as well!
Quick tipâbring PAPER euros if you need to buy anything during layover (coffee etc.) They didnât take pounds or euro coin last time I was there!