What is better for graphics PC or PS3?

No, because the Graphics card in the old Ps3 is bigger than the Ps3 Slim's Graphic card

That's the whole idea behind calling something a "Slim", making things smaller and Slimmer, the PS3 Slims GPU, not "Graphic Card" (Were talking about Consoles here, not PC's) is smaller but that doesn't mean a change in graphic performance, not making it better or worse than the Original PS3 (FAT).