> I would think that it's all the same if you know where to go and what to do to get in.

It isn't. You have to find completely different loopholes in each implementation of networking stacks to exploit them. Anyone running outdated software is always vulnerable to newer exploits, but the thing with Linux is that is audited by thousands of businesses around the globe, whereas Windows probably has back doors for the NSA through some backdoor dealing with the US gov't and nobody can audit that.