I have heard the 401 with the LDA Speed Controller Prototype and the Marketed Model.
I have also heard the 401 using the LDA Speed Controller compared to other Speed Controllers, produced as designs to be DIY produced.
I do believe the LDA is the better as a basic design to a DIY basic design, but have heard a bespoke modified DIY Basic design that was parity or possibly a little better that the LDA on both a 401 and a GL 75.
I use a Nigel Built (Personal Built Model) NSC on my PTP Solid 9.
I know the Idler Drive Sound very well and have encountered many ID's including the 301's, I have heard these models in a large selection of Plinth Designs, but not all demo's are in the home system.
A good selection are in systems I know quite well.
I today find the DD TT, especially in my own case, a Vintage Japanese DD TT, when mounted on a particular plinth type, is much more attractive to my unique preference as a method to replay a Vinyl Album.