That makes sense. After all...
1. It looks better on the PC thanks to improved textures and the possibility of higher resolutions like 1900x1200.
2. Mouse aiming has apparently been implemented perfectly and makes pulling of headshots easier.
3. The online play is free.
4. The game itself is cheaper.
5. You get 5 additional levels.
and 6. You get to fight the Brumak in the pc version.
If you buy the game, then you automatically get a silver account, and can play online...gold accounts (paid accounts) have a few more "features" or w/e but you can play online for free (bottom line).