I think this generation is a flip-flop of last gen processor-wise.
I think MS went for a CPU-centric machine and Sony a GPU-centric machine.
This is in line with what each platform will be focusing on. Next Xbox will presumably focus on CPU-intensive processes (i.e., Kinect, multitasking, AI, etc.). PS4 will presumably focus on GPU-instensive processes (i.e., graphics, animation, physics simulation, etc.).
That being said, there will be logic in each that affords flexibility when needed.
I believe the 4 CU block on the GPU (specialized for GPGPU functionality) primarily represents this flexibility for Sony.
As for Microsoft, I believe beefed up (or additional) SIMD FPUs on the Jaguar CPU side primarily represents this flexibility.
To add to this hypothesis, each system has a memory architecture that is either biased towards making efficient use of the CPU (Microsoft with a large pool of slower DDR3 being balanced with a small pool of fast, extremely-low-latency, coherent ESRAM and DMEs) or the GPU (Sony with a high-bandwidth GDDR5 UMA pool).
I think the design intent for both system is pretty clear here. Knowing this, it is pretty safe to say that the Durango's "special sauce" is beefed-up (or additional) SIMD FPUs on the CPU side.
What do you guys think?