Great question matt,
Let's just say that who ever can answer that question will become rich. Fish are just plain screwy and scents can make them even act wierder. Let's put it this way, if and when you find a scent that works don't always plan on that scent working, you have to be versatile.

But in differences, well they smell different.. No actually there are 4 seperate scent bases that you have and that's oils, amino acids, plants and pheremones. Anise falls into the plant category and why it works I can't truly figure out other than the plant scents that tend to work all have some sort of omega fatty acid in them. You'll also find fatty acids in fish and in all the years, research, and experimenting that I've done I still couldn't give you a definate answer to your question..
Keith