HZJ79 :
Pros:
Stronger transmission (contrary to your research perhaps)
More legroom and cabin space.
Smoother ride due to the front coil springs.
Cons:
Plagued by the wobbles in the front end suspension and steering which need regular repairs.
HZJ75:
Pros:
No problems in the front end.
Cons: Less legroom and cabin space.
Weaker transmission, which is rougher to shift (but is still full syncro)
12v/24v I can't comment on, as they are all 12v in Australia.
Equal mileage and identical condition, I would go for the HZJ75, mainly to avoid the wobbles in the front end. But let's face it, they're both good.