I've only used Seafoam once. I've been a believer in Techron for years. When I travel in areas where it's in the pump gas, I can see a definite and repeatable improvement of 2-3mpg in gas mileage. I've used it a few times as an additive to gas already in my tank.
Personally, I think that one of the best things you can do to keep your bike running well is to ride it.