I may speak out of turn, so correct me if im wrong.
You are correct on pellet count, less weight would mean more pellets in shell, to equal same ounce of shot. This is why you see tss loads using smaller pellets. They can increase the count with the smaller shot and equal the oz of shot. However, the smaller pellets are more dense than lead, which allows for better penetration. So you would actually be comparing marbles (tss) to ping pong balls (lead).
Hope thats correct and makes since. It does to me anyways...