Baitboy, A few years ago I had the pleasure of meeting Phil Pirone (the man behind Pro-Cure) he knew some of the guides I worked with in Ak. and stopped by the resort to say hi. He brought with him gallon jugs of all the scents he produces and gave them to us, I had a chance to try all of them and do some side-by-side comparisons as well as trying them in various combinations, this is what I found, they all caught fish, some though definitely worked better (for me anyways) then others. My first choice by far is either squid or squid/anise together, injected into the bait, I firmly believe the squid put a number of fish in the boat that I may not have otherwise caught.
One other thing I noticed and this may be totally coincidental, alot of the bigger fish I caught that year(over 30lbs.)were white kings, (a biologist once told me a white kings primary diet is squid)
My second choice would be herring or herring/anise oil, didn't produce as well as the squid but it did produce better then the unscented baits, most of the time. Anise by itself also had some good days.
I also tried sardine, anchovy, and shrimp but I can't say they did any better then the unscented baits.
Last thing, the herring seemed to work better then the others for silvers, anise also worked well.
Hope this helps you a little, I hope I don't sound like a salesman cause I'm not, I'm just speaking as a guide who was paid to produce fish and this stuff worked for me. :p