Best Answer - Chosen by Voters
Air New Zealand have I believe the most generous legroom in economy (Pacific class) than any other long haul airline - for me (at 6ft) legroom has never been a problem.
Legroom and good quality food selection, beverages and a professional, relaxed service makes even an economy flight with them a breeze by comparison to some Asian airlines (incl qantas) who pack em in pretty tight in economy - you could be basing your fears of a long haul economy flight on one of those.
Premium economy does offer more leg room than economy (something like 6 inches), slightly wider seats and seats come with a foldaway leg rest. The consul configuration is different (bigger screen?). There is definately more cabin space to lean out and move around in.
The extra luxury and just that little bit more space in premium is welcome over such a long flight time - if you can do it, I'd recommend it. If you dont, at 5'11, it wont be the end of the world.
Hope you enjoy your journey.