One of the best Marshalls I ever played was the 6100 EL34 edition. I love and play music from the classic rock era until the 80's.
I have owned:
Brass 6100 limited edition
1992 EL34 6100
Early 2000's TSL 100 with upgraded board and MM OT upgrade
Voodoo modded TSL 100.
6100 is more versatile because it could sound like a classic Marshall when the gain is halfway and you lower the bass, but it could also sound very aggressive/modern. The top end isn't fuzzy and overall sounds clearer to me.
The TSL100 is definently more classic sounding with the gain at halfway. It has more sag while the 6100 is tighter from what I remember. The clean channels are both good but I remember that I preferred the TSL's. As far as the effects loop go, the 6100 sounded more transparent to me. I only crank the gain to halfway or so on the JCM 2000s because they have more punch and sound less fuzzy. I throw a boost in the front to add more gain.
Voodoo TSL vs stock TSL: The voodoo does sound better because it does reduce the fuzz on the high end and adds more focus and punch to the low end. The highs were not as ice picky as well. The clean channel is improved and the gain levels were not affected. Trace's description on his website is correct. When I updraded the board on the stock TSL, it got closer to the voodoo in terms of quality of tone.
The Brass edition does sound better than the EL34 6100 and it should since it is handwired in some key areas like the power tubes. I think they used some different parts for it that they could not source any more for the other 6100s, (from what I read).
Johan Segeborn has played so many Marshalls and he even thought the 6100 was impressive so don't just take my word for it