PS3 backwards compatibility,

[The Anarchyz]

-All of them have PS1 BC
-20 and 60 GB NTSC have PS2 BC with the Emotion Engine (Hardware)
-80 GB NTSC and 60 GB PAL have PS2 BC with Software Emulation
-40 GB NTSC and PAL don't have PS2 BC

I recommend the 80 GB Bundle with MGS4.