Is there any advantage over using a class over a struct in cases such as these? (note: it will only hold variables, there will never be functions)
class Foo
"(note: it will only hold variables, there will never be functions)"
Never is a big word. Usually "never" means "eventually". Since that's the case, I'd suggest you use a class. That way, when things change, you don't have so much to change.
The Java (and Python) folks have gotten along fine with everything being a class. It hasn't hurt them any to not have these specialized method-less classes that C++ calls a "struct".