But benchmarks, for all their decision-making aid, fail under the best of circumstances for one simple reason: they're not real life. Never more is this true than in Joe Stagner's blog post on whether Windows or Linux, and PHP or ASP was faster. [...] Benchmarks come loaded with all sorts of problems. It doesn't matter if it's Microsoft doing them or Apple doing them; they don't mimic real-world conditions, and any number of factors affect how the benchmarks are rendered.
Keeping these things in mind, Brandon looks at some of the issues he found with how the benchamrks were run, the largest of which was comparing the ASP.NET results (with byte code caching) to a PHP install without APC enabled.