I would consider room geometry and how much fiddling you want to
contend with to set them up properly. I have heard, but not owned,
Quads. I currently have M-L Summit X's, having owned the M-L Odyssey's
and Magneplanars in the past.
I'm well satisfied with the bass especially on the newer M-L's that include DSP. With my "older" Summit X's without DSP, the bass integrates well with 95% of the material I play. With Quads, you might end up adding subwoofers to augment the last octave.
The ESL 11a's are very similar in sound to the Summit X's to my ears. I've found with M-L designs that the lower midrange and midbass tends to get richer and fuller as the panels get wider (i.e. ESL 13, 15, and CLX). Of course, the price also goes up.
I think the main thing to consider is that the ML's behave as a line source due to the geometry of the stators. With M-L's, at least in "normal" sized rooms, you will need extensive diffusion treatment on the rear wall behind the speakers to mitigate comb filtering effects that can cause VERY annoying peaks in response in the upper midrange / lower highs. They also like to be a fair distance from the side walls, as well. Upper frequency response is fairly sensitive to toe-in (mine are pointed straight ahead) and rake angle (adjustable with the supplied footers). They require time and patience to optimize.
I'm well satisfied with the bass especially on the newer M-L's that include DSP. With my "older" Summit X's without DSP, the bass integrates well with 95% of the material I play. With Quads, you might end up adding subwoofers to augment the last octave.
The ESL 11a's are very similar in sound to the Summit X's to my ears. I've found with M-L designs that the lower midrange and midbass tends to get richer and fuller as the panels get wider (i.e. ESL 13, 15, and CLX). Of course, the price also goes up.
I think the main thing to consider is that the ML's behave as a line source due to the geometry of the stators. With M-L's, at least in "normal" sized rooms, you will need extensive diffusion treatment on the rear wall behind the speakers to mitigate comb filtering effects that can cause VERY annoying peaks in response in the upper midrange / lower highs. They also like to be a fair distance from the side walls, as well. Upper frequency response is fairly sensitive to toe-in (mine are pointed straight ahead) and rake angle (adjustable with the supplied footers). They require time and patience to optimize.