Another entrant to the market is the less sophisticated but simpler and cheaper C-head. It has a lot about it that I like....
The C head is a very different concept, that looks similar, so be careful there. For starters, the C head holds only 10-15 solid uses. The Nature's Head and Airhead hold 40-60. So the c-head has to be emptied far more often, which is a huge disadvantage. Empty the c-head once a week, and the Nature's Head or Airhead every 4-6 weeks.
After 4-6 weeks, much of the earlier material is dried out and composted. However after a week, the c-head will simply be a bucket full of fresh poop mixed with peat moss. The Nature's Head and Airhead, with the composting process going on strong inside, quickly break down new additions of solid matter. Emptying the NH and Airhead will be far more pleasant and far less frequent.
The c-head uses disposable milk jugs to hold urine. They won't last long, and will need to be replaced. That might be ok if you are near civilizatiopn and drink milk. The others use a sturdy plastic bottle that will last forever.
The c-head in my view is pretty much a 'bucket with a seat' system. You remove fresh turds, not compost. It also looks cheaper, in my view. The c-head is not the same thing for less money. It's another concept entirely. For another $300 or $400, I'd get a better looking, more convenient proven toilet like the NH or AH.