Charlie, Omega drivers are made for ATI or Nvidia. Omega is a person like you and I, but has a special talent for optimizing the video drivers. He takes the official drivers from the company and "tweaks" them so we don't have to. They come with a nice uninstaller and the best settings for gaming.
The reason that I prefer Omega drivers is that whenever ATI releases their latest CAT's, Omega then takes them and optimizes them for gaming. AW doesn't optimize every time ATI releases new CAT's. I just want the best drivers for my system, after I install the new ones I play all of my games for a little bit and see if there are any improvements in frame rates, less crashes, or better image quality. If I have any problems at all I just go back to the last set I was using.
Hope this helps.