The braking power would be exactly the same no matter what. braking power is a factor of your tire's traction. If a brake can skid the wheel, it get's maximum braking force. if it can't, throw it away.
That said, the Honda MB5 disk will take far more heat and last much longer than a bicycle brake. it's a 9" disk, but much thicker than bicycle stuff and uses the same pad as the rear brake of a CR150cc. it will shed some serious heat. Mine's never overheated, even with my driving.
But I would skip it. the pads are stocked everywhere, but the rest of the parts were only used on the MB5, and it's kind of a semi-rare bike. Go with a CR80 brake. it used larger pads and a more conventional disk that has good aftermarket support.
The whole setup is heavy. An MC disk will weigh as much as the entire brake system for a dual brake Hayes H9 system.
The Dual brake system sounds all kinds of awesome. I'm running 1 of those 224mm rotors on the Monster. It does just fine stopping 300lbs+ combined weight from 50mph, and with the BB7 brakes, it's a 1 finger pull to stand the bike on it's nose. I have gotten the brakes hot enough to melt the cable sheath, though. I recently had the bike doing multiple 1/2 mile runs down some 28%-31% grade hills, abusing the F@#$ out of it. I got it up to temps that would have easily boiled a hydro brake, but the single 224 H9 disk did just fine.
The real advantage of the Bicycle brake is modulation. You're going to have much better brake feel with a single rotor system, and be able to get the wheel closer to a skid without locking up.
With a dual system you'll lose some of the knife edge feel but gain twice the heat dissipation.
With the Motorcycle brakes, you'll lose the light touch and superior modulation on the edge that bicycle brakes give, but you'll gain epic amounts of heat dissipation.
