I've been agonising over this decision as well, so here's a summary of what I have found:
- Physically, the stand is different (and metal vs plastic), with the C9's curved frontage allegedly helping to disperse the sound better, although reviewers didn't notice it. Also, the stand juts out a lot more at the back than the B9 (I don't like this), but has better cabe management as a result.
- Technically, it has a better processor which comes with 3GB of RAM over the 2GB in the B9. The operating system should be a touch quicker, and software updates will be more frequent.
- Picture quality wise, exactly the same panel of course but but the C9 can get a bit brighter. In dark scenes with macro blocking (poor quality video), the weaker processor is less capable of smoothing it out, and so reduces the gamma to compensate. This means there is a little bit of black crush.
So the C9 has some picture enhancements that are subtly noticeable if you have a keen eye. However, I'm actually less of a fan of the C9's physical qualities. The huge box at the back of the TV is annoying as I want mine up against the wall as much as I can without wall mounting it. The wide front part of the stand is also annoying as it leaves less room for things to slot in underneath the TV.
Add to that the price difference, and it's a tricky decision but I feel that the B9 when it hits £999 is the better buy.