I tried converting to vacuum based rcm after someone told me I should never use ultrasonic, as they had done plenty research that show that it wears on the record.
Could you ask 'someone' if he would share his research about record wear causing by ultrasonic cleaning? The best way to learn about what works for record cleaning is to share our knowledge.
From personal experience and study I've heard no reports of wear, however it is, at least theoretically, possible. If someone would volunteer to run a record through a USC with high power transducers for say, 8 hours a day for a week, I'd love to hear the report. Put a piece of tin foil in your USC for a few minutes and observe the perforations.
And does the microfiber brushes actually improve the result? The manufacturers who have “contactless” cleaning claims it is better, and the ones who doesn’t claim not
There's really no such thing as “contactless” cleaning. I suspect you refer to manufacturers who contact the record with something different than other manufacturers contact the record. Ultrasonic cleaning a record contacts it with thousands of tiny pockets of vacuum that implode upon contact with the record, releasing energy. The force of the implosion contact loosens dirt from the groove.
The Audio Desk unit uses two methods to clean, the primary being its four brushes that rotate against the record surface. The ADS cavitation action from a single transducer is fairly mild. A surfactant helps loosen dirt. I owned an original version for several years, cleaned lots of records with it, never had a problem. Eventually I sold it. Specific to it the cons include: you need to buy the ADS cleaning solution which is kinda pricey,and you eventually will need to replace its sponge filter and its brushes. These can be cleaned many times before replacement is required. Put the brushes in a little mesh bag and clean them in your washing machine.
The Audio Desk is a decent machine from a pioneer in vertical desktop record cleaning. Most of the time it will get a record cleaner than it was before it was cleaned and it will do that without harming the record. A five year warranty on a mechanical device is better than you get with most electronics. The company has been around for 10+ years.
In large, the ADS shares the same problems as most other single slot desktop machines:
a) their tanks are small and require frequent water changes, say at least once every 10-20 records, regardless of what the manufacturer says;
b) they do not heat the water - most surfactants for vinyl work better when heated;
c) their tanks are very difficult to clean and accumulate dirt/sludge over time;
d) although some have passive (eg. AudioDesk) and active (eg. Degritter) filters, the passive filters are weak and all the filters are very small with unknown porosity density;
e) few have easy access for using a TDS meter for assessing water quality, although the Degritter does have a separate tank that allows this. Imo it is critical to know the water quality in your RCM;
f) they clean only one record at a time of a given format Perhaps the biggest downside is
g) they dry the record in the tank which means whatever dissolved or undissolved solids are in the tank water get dried on the record.
The primary advantage of single slot ultrasonic desktop cleaners is they are very convenient and easy to use. If that's what it takes to get someone to clean their records, that's a good thing and extends the viability of vinyl analog into the future.