I just found this thread. I have a B50-R and a B100-R. Both of them are fantastic amps. Others here have covered all the tech details, like the 100 having rear ports. Both of them make getting a bad tone impossible. I have used the 50 on small folk music gigs at bookstores, so it's totally useable. I love the 100 for small blues gigs, but it's not quite enough for a rock club gig. It's enough to make me want to buy a B200-R...it has a tube preamp stage!
I just purchased a 200R. It is a fixer upper. The usual issues-mainly, the aluminum chassis is broken loose.
When I finish the repairs on it, I will post a recording with a 100R.
For what it's worth, the 200R is my favorite. For me, it is more powerful, versatile, and it only weighs about two or three pounds more. Love 'em both though.