Posted in the MGS5 thread -
In addition to the ps4 having a 50% more powerful gpu in raw teraflops, the xbox one is *severely* bottlenecked by its 16 ROPS (render output pipeline, the part in the gpu tasked with blending all the pixels and texels together in the final image, Ps4 has 32 in comparison), slow ddr3 memory and not nearly enough embedded memory for the gpu to use. The dev tools seem to be rough too. In addition, the ps4 has a big gpgpu advantage, which probably explains why the ps4 version will have some exclusive weather rendering over the xbox one version over the already huge difference.
Ps4 and xbox one are about as far apart as the ps2 and xbox were if I had to make a comparison, and as this game shows compared to launch games, the gap will grow and grow. Ps4 has nowhere to go but up thanks to its gpgpu capability's, and xbox will keep lagging behind throughout the generation.
3DMark Vantage Pixel Fille rate (from anandtech and techreport)
Radeon HD 7850 (32 ROPS at 860 Mhz) = 8 Gpixel = 153.6 GB/s
Radeon HD 7870 (32 ROPS at 1Ghz) = 8 Gpixel = 153.6 GB/s (7.9 Gpixel from techreport)
Radeon HD 7950-800 (32 ROPS at 800 Mhz) = 12.1 Gpixel = 240 GB/s
Radeon HD 7970-925 (32 ROPS at 925 Mhz) = 13.2 Gpixel = 260 GB/s (from techreport)
The increase between 240 GB/s vs 153 GB/s is 1.56X
The increase between 12.1 Gpixel vs 8 Gpixel is 1.51X
The increase between 260 GB/s vs 153.6 Gpixel is 1.69X
The increase between 13.2 Gpixel vs 8 GB/s is 1.65X
There's a near linear relationship with increased memory bandwidth and pixel file rate.
Lets assume 7950-800 is the top 32 ROPs capability. For 16 ROPS, if we divide 7950-800's 240 GB/s by 2 it will yield ~120
Lets assume 7970-925 is the top 32 ROPs capability. For 16 ROPS, if we divide 7970-925's 260 GB/s by 2 it will yield ~130 GB/s write.
Microsoft's ROPs math includes both read and write which will saturate X1's ESRAM bandwidth i.e. "eight bytes write, four bytes read".
Conclusion, 16 ROPS is not a large bottleneck for 1080p.