I'm struggling to get excited for the three-test series; this year Eng v NZ and next year Aus v GB/Eng. The original idea of the tri nations was that the big three would play each other each year and the idea of the four nations was to condense the comp into a four-week window and include the best of the challengers getting a crack at the big time. That is way more exciting for me than test series.
Imagine a four nations this year or next with Aus, Eng, NZ & Tonga.
I'd be far more excited for a test series if the other nations did what a test series allows and organise other tournaments.
Four Nations was limiting as to what we could achieve, 3 nations plus 1 other while the rest do very little.
For example, a proper Kangaroos Tour of Europe could see:
3-Test Ashes Series
Australian tests v NZ, France, Wales, Italy
England tests v Ireland, Scotland, France
European Championship
Pacific Championship (including NZ)
Compared to Four Nations years where we had:
Four Nations
England v France
Another Australia v NZ test
European Championship (sometimes)
Tours and Test Series allow Tier 2 nations to have both a meaningful competition and test themselves against Tier 1 nations, while Four Nations years we had 1 Tier 2 nation test themselves against all 3 Tier 1 nations while the rest did nothing.
However if it continues like this year and how next year is shaping up with Australia doing shit all, NZ and England doing little but play each other and the Lions Tour being half-assed then I agree Four Nations is a better option.