From Wiki

The major New Zealand Banks are:

ASB (Owned by CBA Commonwealth Bank of Australia)

Westpac (Australian owned)

Bank of New Zealand (BNZ (Owned by NAB National Bank of Australia)

Kiwibank (NZ Government Owned)

National Bank (Owned by ANZ National)

ANZ Australia and New Zealand Bank (part of the ANZ National Group

HSBC (Wordwide with limited NZ Branches)

TSB Bank (No relation to TSB in the UK)

All much of a muchness really and entirely your choice who to go with depending on best interest rates and suitable location of branches. Most banks have a presence on the main shopping streets and within shopping malls. All banks offer the full spectrum of savings, on line banking, credit cards, insurances, ATMs and EFTPOS cash cards. The only bank at present to offer a Debit Card is Westpac. Westpac's Debit Card is a very new and recent introduction to NZ and seems the other banks have yet to follow their lead. Hopefully they will catch on.

Kiwibank because of its Government connections usually offeres preferential interest rates but is not a bank with branches as such, its like Girobank and part of NZ Post. The preferential rates don't, for many, compensate for the inconveniences of having to queue up in the post shop.