We all know CPU performance is much less important than IO performance (file, DB, network), but assuming a large Ruby site and large .NET site both got that part right, and CPU performance does start to matter, what he says sounds reasonable.
Rather than being noticeably faster (lower latency) for a single user, the compiled tier (Java,C#,Go,Haskell,Scala,etc)'s better performance often just allows for far fewer (or cheaper) servers than the interpreted tier (PHP,Perl,Ruby,Python) to be thrown at the problem.
We all know CPU performance is much less important than IO performance (file, DB, network), but assuming a large Ruby site and large .NET site both got that part right, and CPU performance does start to matter, what he says sounds reasonable.
Rather than being noticeably faster (lower latency) for a single user, the compiled tier (Java,C#,Go,Haskell,Scala,etc)'s better performance often just allows for far fewer (or cheaper) servers than the interpreted tier (PHP,Perl,Ruby,Python) to be thrown at the problem.