UA uses a mix of narrowbodies and 767s on the route, while TP tends to use wide-bodies from EWR (although I guess they can sub in an A321LR, though I've never seen that before).

TP takes forever to do food service, whereas on UA it's lights out very quickly - so you get more time to sleep.
You're more likely to get a gate in LIS (vs. a remote stand) with UA than with TP.

TP FAs are less friendly than those on UA, unless you're in biz, then TP service is better.

During IRROPS, UA is much better - many more options via other European cities.