I've had an Avatar G212H with Celestion "Hellatone" 60Ls for about a year now, and couldn't figure out why (besides greater interior volume) it sounded so much more unfocused and woofy than my Legacy 212 cab with V30s. I was under the impression that the Hellatone 60L was a specially broken-in, but otherwise standard, Celestion Vintage 30. Turns out that's true of the Hellatone 60, but the 60L is a
Celestion "Vintage MF" -- the speaker used in Marshall's 280w Mode Four cabs.
"pecially designed to handle the extreme low end that dropped D, D-tuning and C-tuning guitarists demand... engineered to reproduce the balanced mid range and huge bottom end that are a pre-requisite for extreme hard rock and nu-metal sounds"
Overall the magnet and cone seem the same, but the MF's dustcap is noticeably wider and flatter than a V30's...
I bought a barely used Mesa standard 212 recently, but haven't compared it head to head with the Avatar or Legacy yet. I do find myself messing with the amp's controls a lot less often than with the Avatar, though.