Black tanks VS toilet cassette.
Gosh fellows, no-one is more squeamish about the dump than me. When I first heard of RVs years ago, I thought I would never have one.
When I finally did get a tiny pop-top, it had a full bathroom and 2 holding tanks (grey & black). To my surprise, dumping was easy, painless, and odor free. Naturally I always added a half-pint of blue liquid deodorizer before a trip began. To dump I put on dish washing gloves as a precaution then hooked up one end of a fat hose to my RV outlet and the other to the dump site. I pulled the black slide valve and -- whoosh -- everything in the black tank quickly drained out. Then I pulled the grey slide and --whoosh-- the grey tank drained out, cleaning my dump hose in the process. I never bothered to rinse anything because that wasn't needed. My precautionary gloves never even got wet.
The only odor I ever noticed while dumping was a slight whiff of a clean portapotty. I presume that was the formaldehyde. Nothing to see. Nothing to smell. Even my gloves stayed clean and dry. My marine toilet always worked perfectly - no odor from there either.
This basic system of grey & black tank connected to one outlet works so well I always look for that on any RV I might buy. The concept of a cassette toilet was so repugnant I told my wife I wouldn't buy a Hymer Aktiv. Too bad, since otherwise it is a fine design. She liked the Aktiv enough to offer to always take the "walk of shame" in my place. "The Fit RV" folks (James & Stef) have a video detailing their experience with a cassette toilet (link follows).
They were appalled by the stench.

And that was with the manufacturer's deodorizer added. {That detail through a [more] link on their video page}.
I'm hoping some disgusted Aktiv owner sells me theirs cheap and I convert it to a black holding tank (wishful thinking).
My RV of choice (a Hymer Axion) has only one holding tank - a combined grey and black. What's more, it dumps not by gravity but with a pump through a small-ish hose. I don't know how well that system will function.
DougB (still squeamish)