Before you go knee deep in the technical jargon I'm about to spew take into consideration the fact that it really comes down to the application of the hardware and how the developers take advantage of what is available.
The GPU performance is more than just the raw clock rate. The inner ISA and pipeline architectures determine the maximum throughput and bandwidth (your FPS and Resolution are ultimately determined by this).
The Xenos (Xbox 360) and RSX (PS3)are actually quite similar. They are like the same processor from different parallel universes. They both have around the same clockrate. The both have the same number of Render output units. They both have the same number total of pixel pipelines (32). but here comes the difference! The Xenos has dynamic shader pipelines that can be used as vertex or pixel shaders, but the RSX has 24 pixel shader pipelines and 8 vertex pipelines. Again they both have the same number of texture units (32), but the Xenos splits it evenly 16/16 and the RSX sets 24 units to texture filtering and 8 to vertex addressing. The Xenos of course takes advantage of DirextX 9.0c ( plus some extra API specialized for the Xbox 360 ) and the PS3 uses the equal competitor OpenGL ES 2.0. The final difference is that the Xbox 360 video memory is shared with the system memory, and the PS3 GPU has it's own 256 MB @ 700MHz with a special high speed bus direct to the CELL BE.
So in simple terms, they are equal but the Xbox 360 allows for more flexibility in their GPU management.
The story is rather the same for the Memory. The both have 512MB total but the Xbox 360 allows for more flexibility. The system memory is faster on the PS3. But what about the rare case when you want 70% video memory? The Xbox 360 also has that 10MB eDRAM that is essentially smart memory storage that allows for computations and adjustments on the data to be done passively at no cost.
So for the memory I'd have to say the Xbox 360 wins marginally due to it's full flexibility.
Now we go for the processor, which is a really touchy subject. Both have multiple cores. Both use the PowerPC ISA. Both have a general purpose speed of 3.2 GHz. The real difference is in the SPE, or special processing engines. Of which only 6 are available to the game developer. Both CPU's require use of threading and multicore programming which is a complicated task But having to make the best use of 3 processors is easier than 7. The SPE's are very powerful, they can do floating point math extremely fast but require a little overhead to get them started.
As for which CPU is more powerful? The CELL Broadband Engine.
Now for the overall systems there is no doubt in my mind that the Xbox 360 is an easier platform to develop on. But the raw power is highly debatable. I'm not a game developer. Just a game enthusiast. But I can say this, we will not know what each system is fully capable of for another 2 to 3 years. As the frameworks and toolkits get more efficient and powerful the games will become more impressive. As it stands I don't believe from a developer's point of view that the PS3 is so much harder to develop on that ist costs more money.