I am pretty sure that is only on there new speakers, mesa V30's use to be rated at 70 Watts each, now they are just using the normal 60 Watt V30's. It was always known in the industry that they hand picked certain V30's that were a little darker with less mid's and a deeper bottem end. That is what avatar was selling for awhil.
I think since the shift in music scene mesa decided to go with the normal V30's since everyone wants more mids now and the wall of sound scene is gone.
although mesa cabs use a slightly different v30 with a little less mid's and a lower bottem end. If the Marshall has 75's it will be close to the basss response but will sound different then the mesa cab.
Mesa cabs don't use any form of modded V30s. I confirmed this at Mesa Headquarters talking with a rep. He said the cab construction changes the voicing. And the Speakers are regular Celestion V30s.
I would think the Mesa Cabinet would be beter, even if the 1960 uses V30s, because the cabs are voiced differently
The only Marshall cabinet that could yield a gain in performance would be the 1960BHW since its materials used to make it are of higher quality (than 1960/BV/AV),
but the gain in quality doesn't justify the price.