It's a combination of a lot of things. This entire bass line is voiced a bit 'wide and scooped' due to the unique voicing of the active barts, the tweaks on the preamp, the pickup spacing (with the bridge pickup VERY close to the bridge).
The electronics, even when set 'neutral' have a strong voice built in, and the basses put out a LOT of sub bass and upper treble, which can REALLY cause some issues in a live setting (especially with front of house guys used to mixing Fenders, Laklands, etc.... more traditionally voiced basses).
+1 Though, that wood combinations can help (or hurt). To the OP, stay away from ebony boards and/or wenge necks for example, which really bring out the wide, somewhat scooped 'boom and sizzle'. I'd stay away from ash necks also. If you get an MTD with a maple neck, a rosewood or maple board, and some sort of ash or alder body, that does tend to bring in the top and bottom a bit, and be more workable for those who don't particularly want the uber modern, wide, massive low end and upper treble sizzle these basses are known for. I gigged an ash/wenge model for years, and while it often sounded great, I fought with it, and most front of house guys were unimpressed.
There is a reason the gospel guys seem to love these basses. if you are into that 'boom and click' slap tone, these basses will totally deliver. To the OP, if you like that 'big bart soapbar' classic tone, but want lots of midrange punch, the Roscoe basses are kind of the mirror image of the MTD's..... same amazing woodwork, fit and finish and quality, 35" scale and aggressive Bart preamp, but with a pickup placement and voicing that emphasizes pretty much the opposite frequencies as the MTD. Both bass lines sounds great, and 'do what they do', but if you are more interested in low mid punch and articulation, the Roscoe's are quite impressive. They also have a strong tonal personality, regardless of wood choice, but it is a punchy, mid present personality (similar to the Sadowsky Modern... another good option, and somewhat like a 'warmer, more organic Ken Smith tone). Just FYI.