You have to take into account the financial implications for broadcasters. Who pay the bills. What more worthwhile. Two separate comps for the most part offering 2 to 3 games a week to sell. Or a single comp offering between 4-6 games featuring local teams for say 16 weeks? It's pretty easy in the end.
I can understand some of the positioning here. Which is why I want to see a TT competition run independent of the Unions. They should have a vote but they should be just one of a variety of actors. Each team should have one vote. So should the Unions in the form of RA and NZR. Any PE interests should at the very least have advisory positions. The structure of the competition should be in the direct hands of the majority vote. And very early in the piece there should be an agreed road map. Which from my perspective should involve provisions for inclusion of up to but not exceeding 4 new independent (of the Unions) teams in the future in order to bring the number of participants to 16 over a decided upon time frame. With strict criteria in terms of financial backing but not limited on their choice of talent source.
Now, of the nations involved in the future TT structure. Which one has the most room to grow? It just needs everyone to approach it from a distinct commercial perspective.
Without an independent body running the TT as you suggest, I don't think the decision is so easy.
Six teams in Super Rugby AU with 3 games a week with 2-3 guaranteed good news stories somewhere in Australia every week is what rugby in Australia needs right now and into the near future until we maximise its potential.
With the current TT concept to follow Super Rugby AU each year, that gives you two seasons in one, with two peaks, two grand finals, two chances at glory.
The mistake of the broadcasters with old Super Rugby is that they only thought in terms of how many games they could sell each week rather than the bigger picture, particularly in Australia.
NZR has given every indication that they are not willing to change a system that has served their main purpose, which is the ABs. They would rather have less Australian teams than change their system. Although, I would be happy to be proved wrong on this.
But assuming they won't change, which seems more likely, if most Australian teams are getting beaten by NZ teams each week, it's going to feel like old Super Rugby for many spectators in Australia, and we won't be able to build the fan base.
Weirdly, I think Australian players have improved more under Super Rugby AU than they ever did under old Super Rugby. But what we need from playing NZ teams, we could still get with a post-season TT anyway.