Hey Jesper, you know my view. My rim drive is strictly speaking not idler, but an offshoot, and is evolved directly from the Lenco L75.
In terms of tonal solidity, fluid heft, and my tagline "the note is everything", idlers are hard to beat.
Yes, we can argue that as in all engineering, it's the total package that matters. An idler in a rumbly old plinth will die next to a nicely isolated belt drive.
But put that idler in even just a semi decent new plinth and focus on rumble management, and now that idler comes alive.
I've just rifled thru Miles Davis 70s electric jazz period, Bitches Brew to Pangea/Agharta, and the sheer heft and life in these lps is ably portrayed by my heavilly-modded rim drive Salvation.
Where my old belt drive (Michell Orbe, modded w Origin Live motor and Gert Peterson suspension/armboard upgrades) maybe had the edge on airiness, my rim drive just nails the gestalt, the message. Huge solidity, but also fast reflexes, and a real spotlight on density, tonal saturation and certitude.
I love my rim drive so much, that instead of the tedious usual proceedure that audiophiles do in going for a new tt, I invested 5x my original outlay in maxxing it to the hilt, and marrying idler superior strengths w improved performance parameters I only hear in the best belt drives and DDs.
Idlers rule.