It's not the what, it's the why. They are both political philosophies and so both are routed in the way people think about things. Under capitalism the belief is that people do own property and it is actually theirs. To the extent a government takes any of it, it is an exception to the rule and unfortunate. Under socialist philosophy nobody has a right to anything. To the extent that anyone retains any good it is only a matter of practicality rather than any rights that person holds. It is assumed that two very different philosophies would produce very different systems of government if everyone adopted the concepts and a government was built on those concepts. But all the possible governments that could forms from the first philosophy and all the governments that could form from the second philosophy do have some overlap.