- For very obvious reasons, JS (or Python or Ruby) would be slower than Java, C# at number crunching.
- Node.js would handle concurrent connections better than most Asp.Net apps since the framework is non-blocking. Now you could write non-blocking code with .Net, but that isn't how most people write Asp.Net code. OTOH, with Node.js that's the only way you could write an app.
- I am impressed that Node.js actually performed this well in that benchmark. For a dynamic, hard-to-optimize language, being 2.5x slower than .Net (or Java) code is a fairly good result.