I am a big fan of both. Esker Hills is one of the best value golf courses in Ireland, I think. It's built on glacial sandy deposits and feels a bit linksy in places. I love the place.
Carlow is also excellent and always in great condition. It has better clubhouse facilities etc. Very well regarded in Ireland. It would be closer to the route to Co Kerry from Dublin than Esker Hills.
Both are very good bets.
Other possibilites would be Baltinglass, Mt Wolselely (also Christy O'Connor Jnr, American-style course), Adare Manor, the Curragh (one of the oldest courses in Ireland), Heritage GC (don't know what it's like, but it's a new Seve Ballistaros course), The Heath...