^I'm in agreement here as well. Flemming had tremendously detailed notes for those albums, and there's no mention of slaving into Marshalls. When asked if it happened, he vaguely cited "We did stuff like that", which I don't view as confirmation of anything when you get an ambiguous nod from someone about something they did 30 years ago.
When they did slave out to the Mesa Strategy 400 power amp, he made note of it, all the way down to the settings used and into which side
of the power amp. Are we really to believe that someone that
detailed about every aspect of the guitar recording would completely omit something so critical?
I think most of the speculation comes from Kirk's live rig during MoP which features a couple of JCM 800s with the Mesa gear, and studio pics where folks can see a JCM 800 with the other amps...as if they're surprised to see a JCM 800 in a studio in 1985...in Denmark...
So the original posters question, I preferred the Marshall 9200 to the EL34 100/100 when I had them. But, if you want traditional EL34 Marshall tone, you're better served with the latter.