I'm no Windows Cheerleader, but I've got to say you're being a bit unreasonable.  Comparing Red Hat 7 (with Apache I assume) to Win2K Advanced Server for basic web hosting is a bit like comparing how good of a grocery getter a Corvette is compared to a Shelby race car.  One's gonna take a lot more work and still not do the same job.  Now since the product I work on happens to be a web load testing tool (cross platform, natch) I feel pretty confident in saying for pure speed Apache has got it down on almost all other web servers.  Then it becomes a matter of getting it onto a platform where the OS makes the smallest dent in the overall performance so Linux is your winner.  There are reasons for Win2K, but speed isn't it.  Tying it together with your NT domain is really what should be driving those installs.

Now as to the lower bug counts, that's simply a matter of corporate culture and user expectations.  Like I mentioned before, our software is cross-platform and the bug counts are pretty similar between Solaris, AIX, HP-UX, Linux, and Windows.  None of the platforms make it any easier or harder to write bug free code.  However, different modules are used by different types of customers so we know what severity of bugs we can and can't ship with.  The report analysis tool which goes out to every manager needs to be a lot cleaner than the toolkit which goes to your site developers.  The advantage that a lot of Open Source projects have is that they release the buggy code with a little tag that says "not for general use" and the users who want the newest features swallow the bugs for the latest Good Thing(tm).  I wish we could do the same thing, but when people pay for software they expect the latest features and stability all the time.