Also, if you like green, UCD's campus is full of fields, trees, flowers, and a few ponds. Trinity's not quite like that due to space limitations. Athletics-wise, there's a sports centre on the UCD campus with squash courts, climbing wall, courts, gym (you have to pay). There are like 8 soccer pitches/fields to play sports on, a running track with hurdles and sand pits if you're into track and field. You can see the sea/ocean on campus if you go to a 4 storey building. Talked to a few mature Irish students last night and they felt Trinity med program was outdated. Even met some Trinity students in other faculties and they're all very nice. No complaints from North Americans regarding Trinity so far (in terms of education), only from Irish students from UCD. No matter where you go, I think it'll be up to you to make it work.
Edit: Oh yeah we have the ducks and swans that stay on campus all year in the large artifical pond. Sort of like mascots and they can be fun once in a while!