Former IBM technical architect David Shippy, who worked on both the PS3's Cell-specific PPU chip and Xbox 360's Xenon CPU talked about the strengths and weaknesses of both chips.
When asked about which CPU is more powerful, Sippy answered that "It depends... 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. The GPU is highly sophisticated in the Xbox 360."
"At the end of the day, when you put them all together, depending on the software, I think they're pretty equal, even though they're completely different processing models," he concludes.
Shippy then was asked how hard it is to write code for Playstation 3's Cell chip, and he explained that it is really tough, but -if done right- software can "absolutely get the most out of the [Playstation 3] hardware".
"I think some of the bigger game houses that will write more high-level code would really prefer an Xbox 360 -- right out of the chute, it's easier to write code for. I think you can really leverage the Cell hardware technology -- but it is harder to get your head around."