Hi! I traveled from Barcelona-London-Sydney-Christchurch in my last travel to
NZ. I went to British Airways and returned with Qantas. I think Qantas is really better..
For me, the best option is Qantas... or maybe Singapore Airlines, that is really good too and they have a semi-direct fly to Auckland from europe (i think from Milan... but i can't remember exactly)
Good luck with the flights!