"You PC is no more vulnerable the moment you click the tick box"
I know that seems obvious, but in fact it's not quite true. When a security vulnerability is detected and a patch issued, the nature of the vulnerability generally enters the public domain. This means that machines that don't have the patch are more vulnerable than they were previously, simply because the knowledge on how to compromise them is now more widespread.
Like OG, I have my machine set to always notify me, but let me choose which updates to apply, and when.