Another long time Quad ESL owner--since 1973. I recently had my pair restored and use them with a pair of restored Quad II amps with GEC Kt 66s. They sound wonderful-- I hadn't run them in a long time; I had changed to the Crosby modded Quad 63 back in 1990 or so, for many of the same reasons cited by @willemj
I always thought that upgrade was a bit of a trade-off-- a more useable speaker, with fewer limitations, but the original had a greater midrange coherence.
I use these as part of a second system. (My main system is horn/SET-based).
Re Martin Logan, I haven't heard the latest crop- I remember hearing the very large one-- Monolith? in Paris in the late '80s or early '90s. The original CLS? was very well regarded though it was ruthlessly revealing.
Can you listen to both, properly set up with associated components before you make a decision?
FWIW, I think my refurb'd 57 panels sound better with the little Quad tube amp than they did back in the day, when I ran them with a then current production Audio Research tube amp (Dual 75a). The ARC may have been the more useable amp, overall, but there is a synergy with the Quad amps- small and dated as they are, they work magic with the original Quad loudspeaker.
Last thought- verify who did the refurb, how old it is, and whether there is a good protection circuit installed. Those speakers are easily damaged by arc'ing.