If I remember right the big difference is how they are clocked.. The Oval-tech's give you more mechanical advantage (least diameter) at the start of the power stroke (good for racing) and the Biopace give the least advantage (greatest diameter) on the power stroke , to make the cadence even (good for cruising). My knees prefer the apparent even effort around the clock from the Biopace. I can't quite tell from the pictures..

Biopace:


Oval-Tech:


I know a lot of people say Biopace feels like a pedal spindle is loose or bent or something..

Sorry about the thread drift..