IMO they are effective because they hide other scents. I have not noticed a lot of difference in effectiveness among the ones that I have caught fish with. The others act as repellants IMO.
I always carry some anise hand disinfectant, and I use it before hadling any tackle. This seems to make most of the difference. I only use attractant when fishing those nasty smelling swimbaits. I like Gels/pastes like Hot Sauce, so I'm not overspraying into the boat or water. They seem to stay on longer as well.
NoTrollMotor