The real question is, which one should you buy? Here are my picks, in order:
PlayStation 3 (PS3) 60GB version
The 60GB features everything the 80GB model does and has one key advantage: the Emotion Engine.
The Emotion Engine is the brains behind the PS2. The 60GB and 20GB PS3s have one built in, the 80GB version does not. This means that the 60GB version of the PS3 is fully backwards compatible with PS2 and PSone games. The 80GB version is only partially so.
The 60GB version of the PS3 is currently on sale and will not be continued once the existing stock is sold-out. Buy it while you still can.
PlayStation 3 (PS3) 80GB version
The 80GB version is identical to the 60GB version, only with a larger hard drive and no Emotion engine. Both PS3s have built in WiFi and flash card readers, allowing you to transfer photos, videos, and music easily to the PS3.
The 80GB PS3 also comes bundled with a copy of the game Motorstorm, an excellent off-road racing game.
The 80 GB PS3 is approximately 80% backwards compatible, meaning that 1 in 5 PS2/PSone games will not work on it. If you only care about new games, this is the version to get.
PlayStation 3 (PS3) 20GB version
The 20GB PS3 has the smallest hard drive, no wireless networking, and no flash memory card support. It does, however, have a built in Emotion Engine, and is more backwards compatible than the 80GB PS3.
There are still several of these PS3s floating about, though Sony has discontinued them. If you never plan to go online, and can find one cheap, this isn't a bad PS3 to have. Otherwise, go with the 60 or 80GB versions, as this one is simply missing too many features.
Bottom Line
If you don't care about older PlayStation games then the 80GB version comes with a bigger hard drive and a free game.
Finally, if you have no desire to use wireless Internet and do not plan to download any games, the 20GB version may suffice, but I'd invest in either the 60GB or 80GB PS3, just to be safe.
