Stabil and Seafoam have two different purposes. Seafoam is a cleaning solvent and lubricant.
Stabil delays the in tank oxidation of fuel that occurs over time which depletes its potency.
Both the fuel tank and carbs are vented to the atmosphere. The aromatics in gasoline, I think the heptanes (though I could be mistaken), evaporate.
Anyway, gas loses its volatility which increases its flash point and energy content. This is why old fuel makes engines hard to start. Stabil contains ingredients to delay the loss of gasoline's volatility. It is not a cure, though and it's effects are not indefinate.
Seafoam does don't have this ingredient, as that is not it's purpose. Seafoam helps keep in solution the chemical remnants of evaporation of the fuel, and helps delay rust and other oxidation of fuel system components when condensation occurs in the tank.
I don't know how, or if, these two products interact with each other, amicably, complementary, or antagonistically.
Cheers,