I think the idea of rotating Biopace is to get the effect of modern ovoid chainrings (Rotor Q-Rings and O-Symmetric). The newer non-round rings make the biggest gear when the cranks are at their biggest leverage advantage, so the "peak" of the oval will be at 12 o'clock when the pedals are at 9 and 3 o'clock. This is sort of the opposite of Biopace/OvalTech/Cycloid etc. that all put the "peaks" (and therefore bigger gear) equal with the pedals. They intended to help overcome the "dead zone" where the cranks were vertical and riders have little mechanical advantage.

I've ridden both. Biopace feels a little odd when spinning. You get that pulse pulse pulse pulse effect. When mashing, or climbing, I didn't notice it as much. Q-rings, on the other hand, don't feel as unnatural. They felt smoother when spinning, and again, I didn't notice any difference when mashing/climbing.

Biopace and Q-rings are off by 90*. Because there are 5 holes on the Shimano cranks, you can't get exactly 90*, but 72*. Close, but I have heard from a tinkerer friend that it is just off enough to feel distractingly weird.