Apparently the owner of the site that said ps3 version is superior has come out and disputed the claims made by one of the editors saying:
Multiple comments and rumors are circulating around the internet that involve people arguing about which console will have the better version of Grand Theft Auto IV. Comments made by Adriaan on the website yesterday were blown way out of proportion. Both versions of the game offer an unparalleled experience. Both versions offer superior graphics. Both versions will have excellent online capabilities. After playing both versions for hours myself, I can attest to this.
The answer to the question of "Should I get the PS3 or Xbox 360 version?" can be easily answered by asking yourself this question: Which version will your friends be playing online...the people that you want to play the game with? That's it. Answer that question and you will be able to make your decision with ease. It really is that simple.