I know the answer to this one! Whichever bike has the faster rider. Seriously, all this equipment and stuff makes less than 0.001% of a difference. I won races on an old, heavy Centurion with downtube shifters then lost plenty more on a Carbon bike with Ultegra STI and tons of titanium and aluminum (seriously, a magnet wouldn't stick to ANYTHING except the spokes). There are no fastest bikes, just fastest riders.