The title says it all. I know that it's 50w vs. 100w, less features on the SB etc. but I'm thinking more voicing wise. The channel 1 of the SB also seems to differ from the regular BE version.
Small box ch 1 is a plexi type circuit. Very cool for semi crunchy or clean or clean with a bit of dirt.
Othe channel is a BE circuit. The filtering in the amp is a bit like a jtm45 in nature. So not as brutal and a bit sweeter. Comes with loop and line out. That's it.
I played the small box at Musikmesse and own a BE100.
I would say Channel 1 on the SB is more like another version of Channel 2. So it's a seemless progression: clean to crunch in Ch1, crunch to lead in Ch2, and very similar and together sounding. The clean and BE/HBE on the BE100 however are very different sounding channels and there is no dirt to be had in the clean channel. I found the dirt channel on the SB a little less in the low end (which is good IMO).