If it's one of those generators that looks like a coke bottle and rubs the side of the tire and has an incandescent light (at least that's what I think of that goes with "old schwinn") then the only advantage that thing has is not having to worry about batteries -- it has many disadvantages over more modern lights, both generator and battery powered.

If it's a modern hub generator with a LED light, nevermind -- you got the good stuff!