I much prefer 747 for a number of reasons.

1) economy is more comfortable in 747 than in 773 in the event upgrade does not clear.
2) more business class seats in 747 than in 773, and higher ratio of business to premium economy - this means less competition for upgrades
3) LAX on 773 on NZ1/2 is the flight to LHR and tends to have more elite pax - again more competition for upgrades
4) I find meal service on 747 to be faster than on 773 thus can get to sleep quicker
5) seats 7A or 7K are especially private on 747, there is no equivalent on 777