Probably a bit late now but I just got the open-backed smaller one, the UBJ2. You've probably made your purchase already but for the benefit of anyone else looking...
I'll hold back on doing a full review for you till I get mine sorted. Suffice to say that, while it looks good, the set up from the factory is terrible if mine is anything to go by. I'd hope if anyone else has one we can compare notes 'cos the nut on this thing is way too high. Once I have that fixed I can see if it's any good.
I'll get back to you... or write up a review... or something