The bottom end and low mids of the Diezel, with the high mids and top end of the Marshall would be absolutely crushing!
When I heard the Diezel, it reminded me of the heavy guitar tone I dial up on my Mesa/Boogie MarkIV, but with a different top end sound- kind of munted to be honest in comparison to the MarkIV (and via crappy YouTube audio compression).
The Marshall had a better upper mid crunch sound & 'ring' to it.
The Marshall has those high mids, indeed, but you can, make the Diezel sound more sharp, of course.
I really, really liked the Marshall, after the mods ( and even before ), but the VH4 is even more Killer
Ok, it's new (used), you know