But both are, how shall I say, 'insufficiently featured.'
The KLaudio uses only water to clean. Yes, water is a solvent, but it is not enough - it it were we'd not need surfactants. This may be its biggest drawback.
The ADS requires purchase of new brushes and filter every so often (though the brushes can be washed in a washing machine) and it is warranted only with ADS cleaning fluid.
Tanks of neither unit are easily cleaned.
Imo there are superior options. . .
Many thanks for your summary, which was more succinct than mine! One point that you didn't address (I don't believe anyone has) is whether the stronger ultrasonic transducers in the KL Audio unit actually matter. I am not an engineer and can't address that. But logically, if the cleaning is done ultrasonically, I'd assume that the fact that the KL Audio unit has more than four times the power of the Audio Desk unit in that regard should be quite significant. (KL has four 50 watt transducers, and the Audio Desk doesn't disclose the spec, but probably their single unit is rated at half of that.) And the KL Audio transducers fire directly at the LP while it is turning, perpendicular to the surface, while the Audio Desk single transducer fires at the edge and up both sides.
So the KL Audio unit uses four times the strength when it comes to ultrasonics. The Audio Desk includes four barrel brushes to scrub the record but weaker transducers.
But is it significant? Is that an advantage for KL Audio? Or is it overkill and more than is necessary, and the Audio Desk unit is sufficient with only one transducer but also with the cleaning barrels? That is a point that I don't believe anyone, throughout this thread, has ever addressed.
How does all that come out in the wash, so to speak? Which approach results in superior cleaning?
And in the scenario of interest to me, which approach works best for used or new LPs that have already been cleaned on a Nitty Gritty? Which approach would cause the best improvement in sound quality?
With regards to fluid, the new KL Audio unit uses an external jug, and it can easily be a 4.5 liter container -- the same quantity of water as the Audio Desk. I asked KL Audio if the Audio Desk fluid could be added to their unit without causing damage, pointing out that doing so would take one of the criticisms of their unit off the table. My argument to them was that they can say that the fluid is unnecessary and just added cost, but if an audiophile wants to use, well, knock your self out. It is compatible with their unit. That would address one key criticism of their unit. I don't expect to receive a response to my question though.
Finally, you say there are superior options --what are they? Preferably one that is somewhat convenient. The Clear Audio unit referenced in another post costs nearly 50% more at $6,000 and appears to use wet cleaning like many others, but has a "sonic" component but I don't know what that is. Even if I could afford to spend $6,000 which I can't.