They both started out as derogatory and meant the same thing. However, over time geek came to mean 'techie' and is also no longer derogatory. Many people in the IT industry refer to themselves as geeks. It's one of those words where the meaning is or has shifted.
I also like the term 'alpha geek' - the head geek in an IT company, but that's a little more obscure.
wikipedia is always worth a look on matters like this:
http://en.wikipedia.org/wiki/Geek