What's the difference between galvanised brake cables versus stainless steel?
Galvanised ones rust eventually. Especially in the high wear areas. Stainless steel ones don't rust, but possibly don't deal quite as well with sharp curves.

Unless the extra dollar is critical, always buy the stainless steel ones. The bike shops I've been in don't even sell galvanised ones any more because the price difference is so small and the benefit so far outweighs it.