What kind of riding were they doing with these 150 and shorter cranks?
I'm just curious, because in my experience there is a balance (equilibrium?) that is reached at somepoint between the crank legnth and the speed produced from spinning. To me too short a crank arm just means you'll spin out sooner in certain circumstances.
The only benefit to the short cranks would be for a brief burst of speed, like when doing BMX tricks.