I was actually interested in an answer to tilly's question. What is it that makes .Net better for you than the JVM with regards to performance / memory use? Because I haven't seen extreme differences in my situations either.

Here's an experiment.

1. Configure your Windows machine to turn on IIS, running a simple website (i.e. an email form).
2. Restart Windows, access the website and take a note of your system resource usage.
3. Disable IIS.
4. Create the same setup using JBoss.
5. Restart Windows, access the Java version of the website and take a note of your system resource usage.

In all fairness, since this is Windows we're talking about, and there could be special optimizations in Windows to help IIS + .Net work better on Windows than JBoss/Tomcat/BEA Weblogic/Websphere/etc on Windows — go ahead and repeat the Java experiment on Sun Solaris on a Sunfire server instead (with that extra cash hanging out under your sofa cushions).

I wasn't able to perform the experiment on a Sunfire server with Solaris (no extra dough) but on my laptop (2Ghz dual-core prod with 4Gb RAM) I saw 3x more RAM used by the Java setup than the IIS setup.

I could start ranting about how I think Java development is mostly a PITA and should be much easier (look at how simple the language is, for God's sake) — but I won't. Strictly looking at resource usage, ASP.Net is clearly the winner when we look at an out-of-the-box configuration. For .Net, this includes JIT-compiling, for Java it does not. Maybe that's why. Maybe it's the stack-based VM vs the heap-based VM. Maybe it's just that the CLR is more modern and builds on the successes and failures of the JVM in a way that the JVM can't.

I don't know why - I didn't write either VM and certainly won't be writing one anytime soon :-). All I know is that the time it takes me to write something extremely common, say — an email form that allows a file attachment and includes a CAPTCHA — takes about an hour or so with .Net and might take me a couple days with Java. This probably says more about my Java skills than the tools themselves, but the fact that ASP.Net comes with easy file-upload capabilities right out of the box and JSP doesn't (AFAIK) says something.

IRONY: Discussing ASP.Net and Java on Perlmonks.