For nearly all scenarios of use, a cheap Intel or AMD box would destroy a PS3 under Linux. The Cell's single PPC core can't even do out-of-order execution. In the scenarios where they would not, the SPU's would be put to use with specific Cell code -- something you do not find as part of the Linux OS. Sure there are a few apps that do it, but they are rare.
bp
Did Sony back track on not allowing alt OSs installed on the PS3?