Here, they both are similar in I/O bandwidth to breath. However, the R500 has the 48 GB/s EDRAM (256 GB/s effective) to breathe more. This should go someway to alleviate any bottleneck on the GPU with it's UMA design. However, the NUMA design for PS3 has it's inherent advantages with fewer bust contention issues.
It's all swings and roundabouts.
I've spent a lot of time over the years trying to guess the performance of a piece of hardware from published specs and I've guessed the wrong bottleneck more times than the right one.
Until you actually benchmark the hardware and see how it behaves you simply can't predict performance.
Here's an example (purely hyperthetical)
Lets assume that for 1 thread on 1 processor X360 is faster than Cell on either the PPU or SPU.
That doesn't tell us anything about how the system will perform when that task is spread across say 6 threads, the shared L2 on X360 might get thrashed, Cell's SPU's might end up with serious DMA contention. There is absolutly no way to predict.
Because PS3 performs task A better than X360, doesn't mean that X360 won't perform task B better than PS3. Which tells us nothing about performance in an application that requires ABC and D.
My current guess from the published specs would be that they are a lot closer in performance terms and featureset than say XBox and PS2, but that doesn't preclude one or both have serious none obvious bottlenecks.
