I own a BTB1206, a good instrument that I like. I've spent a little time playing a SR1006, also, and thought it was a quality instrument. Fit, finish, and overall component quality seemed on par between the two to me.
To address the question with the BTB1206E's finish: I have one, and it's fine. All the other BRB120x series I've seen (maybe 2-3 others) were also fine. It's a light oil finish, looks understated but classy. The neck finish feels great.
As for the differences, the most obvious one is that the BTB just feels LARGER. The neck is a lot wider, with larger string spacing, and the body is a lot thicker, wider, and heavier. It also feels more angular where it meets your body, whereas the SR feels more sculpted. These aren't necessarily bad things: the wider neck allows for wider string spacing, which makes some right hand techniques more comfortable for some people; it has less tendency to be neck-heavy; and the bigger body may feel more secure to some people. Personally, I chose the BTB almost exclusively because the tight string spacing on the SR series feels uncomfortable to me.
The SRs in general feel smaller and more sculpted. The only downside to this is that they might be slightly neck heavy. Also, you have to be able to play a 16mm string spacing, which feels awfully tight to me.
Sound-wise, I thought they both were somewhat similar, with the SR sounding a little more focused and midrangey. Closer (but not anywhere near) a J bass, to make an analogy. They definitely both share qualitys I think are inherited from their maple through-neck construction; they sound thick, and a little bit compressed, with a strong fundamental, a fair amount of punch, and a somewhat softened high end.
Overall, if you're deciding between these two basses, I'd largely take into account what string spacing and body size would feel comfortable to you.