Thanks for putting up that example. Not sure he his was asking because he couldn't tell the two apart.The fact that you have to ask is a good sign.
Brass instruments sound very interesting when doubled. Mahler and others used 8 horns mainly for 4 part writing with 2 per part. We all know and love the sound of 2 or 3 unison trumpets. You still hear the 3 individuals. At 5 or more you can't really distinguish the individuals, and for brass that's not always pleasing, although big horn ensembles sound interesting.
Even way down low doubled brass sounds interesting. Tuba+Contrabassoon was common in the Romantic period, but Stavinsky had double tubas at times in "The Rite of Spring".
Cimbassi are really tenor instruments, like the standard tenor trombone. The Bass trombone is really a tenor with a bigger bell, thus the low pedal tones sound better. Pedal tones on a tenor don't sound very interesting imo.
The real bass instrument of the trombone family is the Contrebass Trombone, having about the range of the Tuba. Even the very low tuba notes don't translate that well, but work starting around about the E. And sound quite interesting doubled by not its same timbre, but a Contrabassoon, or a Ctrb Bone. And notes that low (on any instrument) need the octave above to really "bloom" thus the Tuba + Ctrb Bone + Euphonium 8va patch.
Anyway, MSB seems to be the best going so far. It'll be interesting to see what Junkie & OT come up with!