What does “Linux developers patch a security hole”? Time until the patch is merged into Linus’s tree? Or more reasonably time until a patched kernel is available in a given distro?
Otherwise a fix in Linus’ tree is about as useful as a committed fix to the Windows source repository.
I don't see why. Users can manually update their kernels in this case. I don't believe that's an option you'll get with a proprietary OS.
With closed systems being able to decide what to disclose and obfuscating their own system, the [power] user is less likely to have actual numbers of anything. Be it how many flaws or how many were discovered internally and placed in the backlog. Then, you throw in some PR requirements into the mix and you'll never have a clear picture of what you're using. Just a sales pitch in a different medium.
This is an important dimension.