I have two bikes, one runs bb's the other runs deore hydros.
If i had to choose between the two brakes for a xc or am bike I'd take the deore hydros. They've got better modulation than my bb's (perhaps because the deores are 2 piston vs the 1 on the bb's) and feel smoother than cable pull brakes ever could not to mention that they're self centering. I just feel more connected to my deores which for me translates into more confidence in the trails. I've had none of the leak issues that the others have mentioned and I've logged close to 3000 clicks on those brakes over the past year.
The bb's are good. They are super easy to dial in and have a ton of stopping power, probably a bit more than my shimanos (may be due to the sintered pads in my deores). They don't feel like budget brakes, and are a good choice but they won't feel as nice as hydros. Period.
Btw, unless you're running downhill or some serious brake burner trails there's no point to 203 rotors, they don't improve brake power, just heat dissipation. 185mm = less chance of warping = quieter brakes. I had a slightly warped 8 inch rotor on a previous bike and it annoyed the hell out of me.