The debate is still open and been going on for years.
There is only 2 advantages for a sinking popper that I know of.
First the extra weight give longer casting distance. Since a popper is a cast and retrieve lure the longer the cast the better.
Second, a sinking popper allows for very fast retrieve. If you retrieve a floating popper too fast it will bounce off the water into the air. A sinking popper will stay in the water even with very fast retrieves.
itsaboat mate...Life is just a boat and then ya marry one !