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However, let's not forget that the 20GB Xbox 360 includes some backwards compatibility support (the 40GB PS3 does not). In addition, you get two free games with the system.
The 60GB PS3 is in an interesting position right now, as it currently costs the same as the 80GB model. For the same price, you can get a larger hard drive and a free game. The only difference? The 80GB has more limited backwards compatibility support. Patrick Seybold from SCEA reminds us that "There are no plans to lower the price of the 60GB model. The 60GB model has nearly 95% backwards compatibility, so consumers looking for that feature have the option while supplies last."
[Update: Chart updated with user suggested information. Updated with minor corrections. Thanks, readers!]