Assuming you don't hold premier status with UA
and are not eligible for E+, then yes, seat pitch would be less in UA
Y. But, in my experience, it's easy to get reassigned to E+ if the flight is not full.
As far as inflight service, NZ
blows the other two away IMHO. But if you're a big fan of PTVs, then you'll be disappointed with the lack thereof on NZ
's 744s. Another disadvantage is the you'll arrive at the over-crowded and dumpy T2
Just some thoughts....