The main difference, in my opinion, is timing of the cams. Twin cam bows must roll over exactly at the same time to shoot their best.

Nock travel used to be a concern when the single cam bows came out, but I believe they fixed that problem.

I also don' t think that the twin cam bows have the speed advantage anymore. There are some very fast single cam bows out there.

I do know that the twin " hatchet" cam bows were alot more stout to draw, and had very narrow valleys, and required almost perfect form when combined with short brace heights.