My Favorite brand is H20.. That's right, Water.
The treatments you pay for.. Might as well put the money in the toilet and flush.
The major source of "STINK" is not the black tank it's the gray, and even that.. I have found the only time I've had a "Stinky RV" was when I forgot to close the valves after dumping on site.. The STINK was coming out of the ground (Sewere system) not the RV.
Now I do, on occasion use a "Digester" product, but only when I know I'm going to be more time between dumps than I am comfortable with.. But normally, and since my wife died (I can go 2 weeks without emptying tanks now used to do it 4x that often when wife was about) . Well, I've not used much tank treatment.