Sta-Bil is a gas additive that stabilizes fuel by preventing separation and helps mix moisture with the fuel so it can be used up as the machine runs.
SeaFoam claims to lubricate engine and dissolve soils and buildups in an engine.
I would purchase the Sta-Bil that you would purchase in a lawn mower section as the SeaFoam is really more for larger combustion engines and not really lawnmower types.
I use SeaFoam or all my mowers it cleans them out so they run better and more efficiently. Use as directed on the can.
Sta-Bil is the best to use.