Enhanced edition is more like expansion than the original game, is even ~250MB lighter. It's also available as a patch for the original game.
Stupid thing is that I own both. I seriously hope Valve keeps them seperate, and doesn't update the old one with the patch!
Buy the new one, I suppose....change notes are here:
Gadgets, Phones, Tablets, Cameras, TVs, HiFi...NextPowerUp
-Only real men play games THIS way.