I've done this route recently on both SQ and NZ. The NZ seat does indeed have more pitch (as others have noted) but I find the SQ seat to have better padding. SQ has larger PTVs and champagne, but NZ has amenity kits, slightly better food and more choice in wines (I say that as a vegetarian). The point about shared lavatories with Y is in my view not a big deal because at least on the 789 V1, NZ only has one dedicated lavatory for PE (789 V2 may be better?) and it's not like they put in a lot of effort to discourage Y passengers from accessing it. While it may depend on the crews and how busy they are, I found the SQ crews did a better job of keeping the lavatories in better condition. NZ also allows PE passengers to use Premium Check-In at AKL but I actually found it to be busier than just the standard self-check in queues.