Disc.... Leverage.... Stoppies.
 

So, I had a Mongoose (walmart) with 29 inch wheels and a 160 mm front disc rotor and Zoom caliper with 3 bb's making it work. Well, I wasn't happy with the braking power of the front wheel, so a 203 mm rotor was installed along with a offset bracket for the caliper. BINGO!!!! Instant stopping power. Even have photos of me doing stoppies on the bike with no other modifications. All I can think is the extra leverage from 160 to 203 is enough to throw you over the bars.

So.... What is the point of spending big bucks on high end calipers with multiple BB's when the cheap caliper with simple non-metalic brake pads the size of a dime hooked up to a big rotor can easily send you over the bars.

Want extreme stopping power? Go semi-metalic.

I think expensive calipers are greatly over rated. That being said, I have Avid BB5 calipers on all the bikes now.

What's a BB?

Maximum stopping power is rarely the most important feature of a brake, it's how you get there. More expensive brakes tend to feel nicer, more linear. And require less hand effort for the same amount of braking.
But if you're happy with inexpensive, good for you.

BB5's are budget, (yes there more than some, but your saying their expensive, and relative to expensive calipers, their not)

Would be more concerned that with the 203mm rotors, and if your fork can handle them? as often forks (less DH ones) are rated for a max 180mm rotor.

As #debac mentions, its not stopping power that's important it's how it's applied, modulation/feel is a key factor into how well the brakes (and you with them) work.