Having 8gb gddr5 does not suddenly make the durango worse than it was before.
This is a quote from Andrew on B3D on Sony's gddr5 choice
He is into graphics dev, and has published quite a number of articles on rendering etc.
The move to 8gb from Sony just means that they are now on equal footing in RAM size. Whatever difference in FLOPS will not be significant enough that it will be readily identifiable.
1. Anytime someone says "X is overkill" when it comes to home consoles they're full of shit. Everything you give a developer will be of benefit to them, any time you give them something that is easily accessible it will benefit them that much more. Doubling the unified memory pool is hugely beneficial as a result because it's a big, easy to use tool.
2. There is no caching system that substitutes for high bandwidth pipes across the board. Any attempt to even bridge the gap via a caching system eats up developer time in fine tuning and tweaking.
3. Most developers acknowledge that Sony had a ram advantage when it was expected to be 4GB of GDDR5 since the performance jump thanks to it's higher bandwidth would be more beneficial than the sheer quantity MS was offering. The quantity advantage has now disappeared and Sony's bandwidth advantage has remained the same. The "slight" edge that was generally accepted on the ram side of system design has now grown.
4. Of course it doesn't make Durango worse than it did before, it just makes the PS4 better, and in a comparison of the two the delta has grown as a result.
5. The currently rumored GPU divide is significant. 1.8 TFLOPS to 1.2 TFLOPS is not massive, but it's a meaningful gap.
6. The downside of ALL of this for MS is that they now seem to be the one using esoteric hardware. An ESRAM cache to make up for unified DDR3 requires more work for developers. A more heavily modified GPU than the standard ATi offering requires more work for developers to familiarize themselves with the capabilities and to then exploit it. Any additional hardware they might have layered in will do the same. Further, these customized tweaks add to system complexity, which directly impacts cost.
Sony has built a developer's console and it is by proxy a gamer's console. This is the result of Mark Cerny being tasked with it's design. MS doesn't appear to have someone like Cerny to do the same job for them, and executive interviews paint a company with no particular interest in doing that if they did. That is emerging as the X factor of this next generation.