I had John's wonderful Tap linestage, which used S&B transformers as you mentioned, and then went on to another great linestage, the Flora, that used autotransformers in its volume control. So, to answer your question either device used and set up correctly offers great sonic performance and from a practical veiwpoint are the same.
tvc vs avc
from a practical standpoint, what is the difference between a transformer vs autoformer based passive volume control? Bent Audio has moved to Slagle autoformers to replace the unavailable tx 103 S&B transformers, and apparently thinks they work at least as well.