I'll mention ahead that this one's aimed more at picky people, and that in the last forum I posted this at, most people said they couldn't see a difference (pretty bad eyes oO).
For a better comparison, open both images in tabs, and skim through them:
What's the trick? RS lets you change the Anti-Aliasing settings, which smooths model (NPCs, crates, buildings) edges, but not the Anisotropic Filtering, which sharpens the model's textures (walls, roads).
How can you change the settings yourself? Look for the Anisotropic Filtering option in your graphics driver 3D settings page, and change it to x16. What's the performance hit you wonder? I measured 2 fps difference on my laptop's Geforce 8400 (which is a piece of poop).