We have a cheapo
Wild Country unit that works well enough. We've only ever used it with a bio treatment so that we can pour the contents into pit/composting toilets or septic systems without destroying the toilet (which is what can happen when you drop the AquaKem or Thetford stuff in).
The problem with the bio (enzyme) stuff is that it really stinks. The chemical itself is fine but even super-dosing the toilet doesn't improve the smell. The Thetford chemicals at least kept the place smelling nice. We didn't want to go back to that, so we tried something else...
Napisan. Bloody hell, it works too. It's supposedly safe for septic systems as well, but I'm not yet 100% sure so I've just used RV dump points so far. I've also discovered that the active ingredient is stronger in the darker labelled Aldi version.
Smell? It's fine, as long as you follow the "directions" which I'll repeat here (we learned this from a blog somewhere).
Mix in a capful with 1 litre of warm water, pour it into your freshly rinsed tank. Mix another capful with 1 litre of warm water, pour that into the top tank then fill with cold water. Every day, pour half a capful into the holding tank. When full, empty it appropriately and rinse - most dump points have hoses attached.
If we ever wanted to buy another toilet we'd probably get
this one. Height is an advantage - means you don't have to bend the old knees as much!