They are both very extended and transparent. Deep resolving bass Smooth. Grain free highs. Exceptionally quiet. Large image. I thought the ZOTL40 with its EL34 tubes had a little more forward midrange “bloom”.
I thought they lacked some “flesh on the bones” if that makes sense.
sidebar comment and response to @tvad's post above
i also have the lta zotl40 ref - the amp is definitely among the most transparent, 'insightful' tube amps out there... certainly the most transparent i have heard and i have had many many of them... the degree of midrange and midbass bloom from that amp can be improved by using mullard old stock el34's or (their close equivalents) and careful selection of input tubes