I think its a wash. I've used both, and I kinda prefer TAP. I haven't done the A321 yet, but the A330 Neo is excellent, and I/we at least, have had great cabin service even in coach on TAP. I've found the TAP cabin crew perfectly professional and super efficient, never had a bad experience, although some people have said otherwise. As another amusing thought though, I've gotten higher UA Mileageplus credit from a TAP discounted ticket than I did on UA.

UA is fine. So is TAP. UAs planes are bit tired though.....