Which new OS should I move too?

I need a new OS on my main box. Something technical that will give me a more in-dept knowledge of the technicalities of Unix and Linux.

I'll be attending a grey hat boot camp in a few weeks. What should I compile?

I'm a newbie to network OSes and the only Linux I use extensively is Ubuntu.

>>7
This is a bit outdated, but it still outlines the core philsophical differences between at least FreeBSD and Linux based systems. http://www.over-yonder.net/~fullermd/rants/bsd4linux/bsd4linux1.php

I cannot say for NetBSD or OpenBSD. Though, I can tell you that Theo de Raadt is a crazier nutcase than Stallman is.