What's obvious from Labour's result is that having multiple segments of the party voting can highlight issues that parties generally don't want highlighted. Compare this segmentation with the last elections for the leader of the Conservative Party in the UK. It was a clear result thanks to only having members of the party voting (then there's the crazy system Canada's Conservative Party uses - each electorate organisation gets 100 points to vote with, which were proportionately allocated depending on how members in the electorate voted). Crazy or not, the principle of one member one vote is observed by both parties.
Sadly, this principle has yet to make it to our own National Party. As Toby Manhire notes in The New Zealand Herald:
If I were a member of the National Party, I'd be wondering: how come I don't get to vote on the leader of my party? Take it from Judith Collins: while excoriating Labour's "foolish exhibition of faked friendship" this week, she also observed that "political parties should always be about their members".Toby then cites Canadian research pointing to the fact that parties tend not to change the rules unless they've suffered a major electoral defeat. But it doesn't have to be this way - now's the time for National to decide the rules. It would be a great contrast with Labour's rules, and would energise the membership base (I seem to remember a TV One report that Labour's membership had been boosted substantially by the election). It's time for party primaries.