I received my Brahma yesterday. I played it along the plexi module for a while and was very positively surprised.
I like the plexi. It has this characteristic Marshall bite and with a maxon OD-9 as a booster, it sounds autentically 70's. Instant Page!
I was really curious to see how it would compare with the Brahma. I knew gain would not be different but I was suprised how different the voicing actually is. I can't guarantee that my plexi module hasn't been modded tough.
The Brahma isn't as trebly as the plexi, by far. I actually have a marshall SLP re-issue so I AB'd the modules and the amp itself.
In all fairness, the plexi module sounds a lot closer to the "real" plexi (the SLP re-issue is no highly rated among plexi lovers). Especially because of the upfront high frequencies.
The Brahma, also has the marshall growl but I found the highs much better integrated in the overall sound instead of being "in your face" like the plexi.
Ultimately, I came to understand that the plexi is a very good emulation of the characteristic plexi sound while the Brahma, is the emulation of a single particularly good plexi (Lynch's one as stated previously). And very good plexis are known and cherished being more flexible tonewise and smoother sounding than regulars plexis.
I also noticed that the Brahma blends much better with my other modules. The really vintage tone of the Plexi (and the JMT that I also have) actually made it tough to switch from one module to the other, as the difference in voicing was really obvious to the point where it became distracting.
I checked the Brahma against the Mr Scary module and they go together really well. Voicing wise, they are comparable. The scary has a more compressed sound and a lot more gain, but switching from the Brahma to the Scary, sounds like switching from one amplifier channel to a higher gain channel on the same amp. Definitely a good pair allowing to cover many marshall tones from Clapo's bluesbreakers leads up to Dokken's 80's albums.
I use the Maxon OD-9 as my main booster. It is not a neutral pedal and tend to add some smooth mids to the sound. For all marshall typed modules, it works really well. With the Maxon, the Brahma doesn't become a gain monster. But that's fine as that's Mr Scary's job!
. With the gain around 3 o'clock, the Brahma's gain is in the AC/DC zone. With the booster on it does the higher gain stuff up to the early Van Halen sound very well.
Overall, I would recommend the plexi for people who really want "70's" stamped on their sound signature. The Brahma is also marshall, but timeless marshall if that makes sense.