yeah, I read some different opinions and I will not try to justify why anyone would state that, other that they had units of different conditions, or did not perform true A/B listening.
In my system where the amp would be the only variable, a properly restored B-2 or B-1 will sound same or better in most situation than a B-3 or B-3 duo.
The problem with the B-2 or the B-1 is that they require lots more work and some simplification to bring them back to prime. The simplification part would actually allow for by-passing some of the selector functions and streamline the signal path. This brings them to a simpler signal path level, similar to that of the B-3 (or TA-N7, JM-S7, TA-8550, BA-1000, SIT-3, for that matter).
I spend countless hours of A/B listening to most V-fet amps ever made.
One thing I can say is that ALL of them are very engaging, where some would sound different than others or have more authority, but the differences are subtle. Another out-right statement I can make based on my listening impressions is that none of the other amps matches the B-1 in terms of sound stage and 3D of depth. The low-end of the B-1 could be blurry if the wrong type bulk caps are used. This is true for all the others, but it is more noticeable with the B-1.
An important callout is that during the restoration, if the wrong replacement parts are used, that WILL impact the sound signature of the unit and not in a good way.
For my restorations, I keep a well preserved and mildly refreshed original unit of each model as frame of reference for the other units I am restoring. During the restoration process I do not introduce any components that would negatively impact the sound signature of the original. Sadly, replacing components just for the sake of replacement, is a practice wildly popular which in most cases would actually cause a "rebuilt" unit to sound worse than the original.
