Found a comparo article at Gamespot!
http://www.gamespot.com/features/6202552/p-4.html
Here's the article:
Grand Theft Auto IV finally made it to the PC; unfortunately, it arrived with its fair share of performance problems. At times we experienced massive texture issues that caused the game to render nothing but water with our lonely car sitting on top of the waves. The game's lighting and shadowing also rendered incorrectly, creating nasty shadow bands over the buildings and streets. We didn't include images of the graphical artifacts because we didn't see them frequently enough warrant documenting. Generally GTAIV runs fine, and RockStar has released a patch since our testing that should clear up most of these visual oddities.
GTAIV is the one game we tested for this comparison that didn't let us max out the image-quality settings on the PC. At the moment, no video card has enough RAM to load up high-quality textures with high resolutions at maximum-quality settings. We could, however, load up medium textures with very high-quality rendering and mostly maxed-out sliders. Surprisingly, GTAIV does not support antialiasing in any form, which heavily detracts from the game because the city environment has a lot of hard edges, wires, and random foliage. Even with all the problems,
GTAIV looks better on the PC by a wide margin. The PC's high resolution and draw-distance levels keep higher-quality textures, lighting, and transparency effects visible farther into the distance.
As you can see from the comparison, the textures look much more smoother compared to the other consoles, and this is only set at a "medium" detail setting!!!