Well I just spent half an hour out there, plugged both cabinets into all 3 amps and turned them up to 7 ish.
I would move back and forth standing in front of each cabinet and listen to the differences.
The greenback ax cab isn't as loud as the V30/T-75 cab, but I'd assume that's a wattage difference? Maybe it's an efficiency difference?
Seems like pretty similar tones in high gain mode, the greenbacks seem to have similar bite and growl, and are a bit smoother overall I'd say.
The t-75/V30 combo has a rompier mid-range and maybe a tad more bottom thump?
Together behind any of the 3 amps they sound amazing! Can't hardly play without smiling at the combined roar!
Seems like as a whole stack they make my 3 amps sound a bit more similar than different.... Perhaps the sound spectrum gets smoothed out by the 3 types of speakers working together? Just my take on it.
Lots more to learn once I get a mic in front of them separately and record some tracks!
Pretty pleased with it so far!