I was reading a comparo of some 80 cartridges from 1979 or so (HIFi News And Record Review in UK did it, I think - I have re-print of it).
It's quite a tell-all report - that type of reporting just isn't done anymore...and maybe never done as broadly here in the US.
For most of the MM/MI's in the study, fluid arm damping was recommended. For most of the MC's, it was not recommended. I had always thought arm damping was beneficial - so I applied it according to my turntables owners manual for the past year - equal to the tracking force of each cartridge. My arm is oil filled and it has controls for both horizontal and vertical arm damping - so I can really tailor the amount of damping to each cartridge.
It's a whole world of tweeky crap I hadn't wanted to know about

, but there it is all the same. Lately, I've been experimenting with it.
The effect ranges from sublime (Grace F-9) to astounding (both Grado's). I keep finding the same result as the magazine does...the Denon DL-160vdH benefits from it and the Ortofon X5-MC and woodsyi's Benz MC-3 don't. In fact, in a twist, the MC-3 is notably
worse off with damping...it sounds overdamped with
any damping. The Ortofon sounds about
the same either way. The Denon is
slightly better with it.
Has anyone else with fluid damping found anything like this, as well?