Ed130 said:
Ouch, don't they both share PC architecture?
Yes, but.
The Xbone uses a slower GPU and RAM, exactly how much slower the GPU is Microsoft refuse to confirm, but when all they'll say is that it's got '853mhz and 5billion transistors' that's not an overly good sign.
More importantly, the Xbone uses normal DDR3 RAM with a 32MB esRAM chip on the processor itself, which gives it a maximum bandwidth of 68.3 GB/s. By comparison the PS4 is using GDDR5 (which is broadly DDR3 but with a much higher writes per clock cycle to handle graphics processing better) with a maximum bandwidth of 176 GB/s, when it comes to handling large texture files and high screen resolutions, that will make a difference.
Also, the Xbone reserves 3GB for system use, so 5GB is available to games, we don't yet know how much the PS4 wants, but if it's equal or less space then the performance gap will widen over time as games become more demanding and screen resolutions go up (these consoles will probably be seeing 4k screens by the end of their life cycle).
TL,DR: Microsoft are using normal PC RAM whist Sony are using more expensive parts made specifically for graphics.