Why should I buy the ps3 slim over the older version?

People keep saying the slim is so much better, but I cease to see why. I mostly have ps2 games, and they will not run on the ps3 slim(from what I have heard). That is one of the reasons I wanted to switch from xbox 360 to ps3(also because if infamous 1&2, kill zone, etc.). So, can anyone tell me why the ps3 slim is better than its older versions.