I've been using generic slick, galvanized cables for around 15 years. I like them better than stainless because I can solder the ends. That way I don't have to mess with end caps and I can even remove and replace the cable through the housing if I need to.

Actually, I do use stainless tandem cables because I buy them one-at-a-time. Functionally, I haven't noticed any difference whatsoever.