What's the difference between all Playstation 3's?

I tried to look for the differences between 20, 40, 60, and 80 gig models other than price points and drive space. Can anyone help me please? I hear some have more USB ports, etc. I can look elsewhere obviously (on the net) but I'd rather get real answers from real time forumers who own all models.

And what's with this "emotion engine" that some have and some don't have?

20 gig is long gone and you shouldn't want one anyway.

40 gig has no memory card slots for sd compact flash and memory stick, two usb ports and no backwards compatibility with ps2 at all. it plays ps1 games, though.

60 gig is discontinued but you can find one on ebay or something easily. It's got the memory card slots, four usb ports, emotion engine(which runs all ps2 games by hardware emulation)

80 gig has the mem card slots, four usb ports, and software emulation for ps2 games which plays less than emotion engine hardware.

You forgot one thing.

The PS3 40gig uses a much better cooling system, and modified chipset.

The 40gig consumes 135 watts compared to the regular 200.

This does make a significant difference in the end. Considering it also causes the system to run quieter.