So I'm conducting an experiment and may give samples of the results later. I'm taking a still sealed record I have and going through this process:
TEST SUBJECT:
Ben Vereen - Here I Am (1982) [Virgin copy of record still sealed]
For each playback, my stylus gets a Magic Erase dab... all recording captured with Adobe Audition 3 at 96000 Stereo 32bit float using ASIO4all drivers at identical recording levels.
Side 1: Virgin Record- Your basic drop and play. I opened the record and am recording it dry. (NO PRE-CLEANING OF ANY KIND ie sink, static brush, nothing)
Side 2: Virgin Record- I'm playing side 2 ALSO WITH NO PRECLEANING. The only difference here is that I am "wet playing" it by my usual playback of records method... I take a microfibre cloth and, while spinning, dampen the grooves with 90% isoprop, then using the other end of the cloth, wipe down with disilled water. I make sure the whole surface (save the label that is), is very wet, but not spitting water onto the turntable from centrifugal force.
Tomorrow, AFTER I've given the record grooves 24 hours to "heal", I will do my sink washing regimen, and then repeat the steps, and provide samples of what I get. I know this experiment would only suggest very approximate results vs EXACT, but I think the experiment would be a useful guide. If anyone can provide reason to switch tomorrow's experiment (that is, wet play Side A vs B for some supported reason), please let me know.
Already from the monitor I am hearing pop and crackle and can visually see paper sleeve artfacts on both sides. This created surface noise on my Side A dry play. It was greatly reduced but still audible on Side B when wet played...
Plus, just yesterday I picked up VERY dirty but unscratched 80'd pop records from a local shop and hand washed them and wet played them. There was virtual silence in the lead in grooves and in between songs; you can guess that the ssongs themselves were flawless. A 1940's jazz record had SLIGHT surface noise when given the same treatment, but I'll see how it sounds after a woodglue "facial"...

So I'll keep you posted, but already it seems like a proper clean is best for ALL records.