Hi Steve,
IMHO, the two Otari's (BII and BIII) are very close to each other and I believe to be some of the best in the world---now or "ever". I have a few of each example that are all tuned up to comare back and forth. Also---Ki Choi can confirm the merits of the Otari's, as you know he has just about every deck ever made---Studers, Sony's, Technics, Otari's, you know the routine-----
The BIII is slightly better then the B2, in these areas:
1) Is slightly smoother and quieter as a transport (better at searching too---see "logic" below)
2) Sounds better stock and records better stock (I use my BIII for all live recordings and dub recordings over a BII)
3) Has better logic controls (a few more settings and is "smarter")
4) Just "feels" more refined (think "Studer" vs. your favorite vintage deck) and is laid out better and is more "user friendly"
Both are great decks and as 80% of the parts interchange between the two (even the whole headstacks!)---- it makes them extremely worthwhile!! Very easy to get parts too.
The thing is you have to be PATIENT when searching for one. There are SO MANY. And the difference between a pampered BIII and a beat up BII is lightyears.