Former IBM Architect: PS3 and XBox 360 Power is Fairly Equal
Former IBM technical architect David Shippy, who worked on both the PS3's Cell-specific PPU chip and XBox 360's Xenon CPU has discussed the power of each system.
He couldn't give a definite answer on which system was powerful and laughed it all depends. The conclusion that he come to was that overall they are fairly equal even though they use different processing models.
To quote: But Gamasutra also asked him about the relative power of the two systems - since he worked so intimately on them, does he have an opinion on which was the more powerful?
"I'm going to have to answer with an 'it depends,'" laughs Shippy, after a pause.
"Again, they're completely different models. So in the PS3, you've got this Cell chip which has massive parallel processing power, the PowerPC core, multiple SPU cores... it's got a GPU that is, in the model here, processing more in the Cell chip and less in the GPU. So that's one processing paradigm - a heterogeneous paradigm."
"With the Xbox 360, you've got more of a traditional multi-core system, and you've got three PowerPC cores, each of them having dual threads - so you've got six threads running there, at least in the CPU.
Six threads in Xbox 360, and eight or nine threads in the PS3 - but then you've got to factor in the GPU," Shippy explains. "The GPU is highly sophisticated in the Xbox 360."