If you look at the central processor in Microsoft's (MSFT) Xbox 360 you will see something that can trace its ancestry right back to the Intel 8086 of 1978. Over its evolution this has forced endless fudges and compromises. An analogy might be trying to build a working supertanker on the plans of a model rowing boat. And the 360 itself owes its architecture to the IBM PC of 1981 and so carries with it the accommodations that this architecture imposes. These factors, ultimately, must impinge on the working of the console.
Compare that to Sony (SNE), who were able to design the processor and the console it is in with a clean sheet of paper. The Cell processor, designed jointly with IBM and Toshiba at a cost of $400 million is the state of the art in processor dessign. It is scalable, highly flexible and excellent at distributed processing.