It's definitely between Nelsen and Reid ability and performance wise.
I find it hard to say who is better. Both have been just as important to their AW's sides.
Nelsen gets the edge for me because he's been tested in the World Cup Finals and for his immense leadership abilities on and off the field.
Tommy Smith has had a solid career at Ipswich but is somewhat behind the above two AW's legends.
From years past, most pundits I think would rate Ceri Evans and Malcolm Dunford as two of our best.
Ceri Evans received 56 A international caps and played 116 matches for Oxford United in the second tier of English football in the late '80's and early 90's. His pro career would have been longer and he was probably good enough to have cracked the top league but he always had to balance pro football with a second career as Oxford University scholar (Rhodes scholar and later one of Britain's top academic psychiatrists). Was only 17 when he gained his first AW's cap.
Malcolm Dunford was the other top NZ centre back of the mid-1980's to early 1990's. He never played overseas but was good enough to.
After that you're looking at Danny Hay who was part of a Leeds United squad playing Champions League.
And Ricki Herbert - from the 1982 All Whites and the first NZ centre-back to play professionally overseas, at Wolves for two seasons in the mid-80's under Tommy Docherty.