If you want a Mesa sounding distortion get a Mesa, u want a Marshall sounding distortion get a Marshall.... it's as simple as that! Just like if you want a Gibson Les Paul sound get a Les Paul and if you want a PRS singlecut sound get a PRS singlecut.... There are no comparisons even though they are both shaped and supposed to sound the same. Big difference between the 2.
No way a Marshall JCM 800 is going to sound like Mesa Dual Rect.... Hype, maybe but once u've tried a Mesa, you'll just go GAS crazy. High gain new age distortion with vintage Marshall sounding distortion. Capable of duplicating almost any distortion sound you can get just maybe British sounding crunch.