Credits for this goes to Steam user XenoBrain which mention in discussion but in my opinion its very important information so I decide to post it here.

It's been mentioned here that enabling anti-aliasing disables shadows. It feel it's important to draw attention to this--in fact, it does more than that--it reconfigures the entire rendering pipeline. You'll miss HDR, bloom and many other subtle touches that enhance graphical quality.

Essentially the differences that have people complaing that the 360 version looks better than the PC version, this is rectified by disabling anti-aliasing.

Do it in the config tool before you boot the game.

If you want anti-aliasing, it can't be forced in the control panel but a tool such an NVInspector is capable of forcing it with right configuration, otherwise you'll have to use FXAA/MLAA etc either from your graphics card's control panel or your favorite injector such as SweetFX.

But I would recommend to use downsampling[www.neogaf.com] e.g. set your resolution higher than standard 1080x1920.