Don't have much experience with MC90s, thats why I'm trying to find out more about them.
CL80s are a continuation of the original 80w speakers, not a reissue by any means. Compared to CL80s (which I hated at first, but warmed up to after I really cranked them), they both have that clean, accurate quality, but the old ones have alot more British sounding midrange, very very in your face. So in your face that I did not like them in my front loaded cab, while the CL80 was fine in there.
Its just very bold, with a bit of that EV brassy hardness to it. Its the only Celestion I've tried that is more aggressive in the mids than a V30, but it has loads more top and bottom than any V30.
Thats why I'm hoping the MC90 will be close to it, as many accounts say the MC90 and old 80 watter are much closer to each other than either is to the CL80.