Call me crazy but I really like the 757-200 when I fly to Dublin. It is cozy and the AVOD is good. The seats are fine and the bins are a decent size. In comparison to the 767 I occasionally get to LHR with looped video on a tiny screen and the overhead bins that are the stuff of stand up comedians, I say the 757-200 is perfectly adequate for TATL. Besides, it allows UA to offer more frequent service to DUB.
I remember a few years back, maybe 2011/2 I was flying DL to Dublin a lot and they had an ancient relic on the route. I think it was a 767 (please correct me if people remember). They bought it from some outfit in Florida perhaps and it was domestically configured and was missing mid cabin toilets. Again my memory isn't good, all I recall is that going back to the UA 757-200 was a dream in comparison.