There's still room for improvement in both of them, too. If you want to have a lot of connections open, you have to choose between lots of threads with blocking

There's still room for improvement in both of them, too. If you want to have a lot of connections open, you have to choose between lots of threads with blocking I/O, or using event-driven I/O, or using some kind of magical light-weight cooperatively multitasked greenlet/fiber thing. As Erlang and Haskell show, it's totally possible to combine an event-driven I/O subsystem with lightweight user-space preemptive multithreading that supports a huge number of threads, takes advantage of multiple cores, and doesn't need to worry about blocking-vs-nonblocking magic. I would love to see that in a more mainstream language.