With every form of potoato, you can have cheese, same with onions!
Plus there are soooooo many more ways you can eat cheese, therefore I say cheese is more versatile! lol!
I'd have to say tomatoes, even though I hate the things. They are the basis of many sauces, are a crucial ingredient in stuff like chilli, spag bol, curry etc and can be added to salad, made into salsa, grilled on a full english... the list is endless!