So in the past there has usually been a compute winner and a gaming system that's easier to develop on. In the 8th generation of Video Game Systems we see a move toward x86 (Will ARM be a player here next gen?) sort of mini computers. However, these are much more integrated leveraging its advantage over actual computers.
The PS4 utilizes low power but out of order optimized 8 core x86 which can apparently turbo to 3.6GHz. The APU is integrated and shares a pool of 176GB/s GDDR5 Memory which in the past has only been used for video ram. This cuts down on the need for RAM and will allow the system to compete against higher priced gaming computers. At $399 the PS4 offers bang per buck with an optimized unified architecture and a 1156 shader Radeon GPU which has been optimized for tessellation and GPGPU.
The XBOX One is a lot like the PS4 but it lacks some deep level integration between the CPU and GPU in the APU, the parts are slightly less powerful, and it utilizes 32 MB of 107/GB/s ESRAM. I do not understand adding the ESRAM. It is not enough to render a 1080p 24bit picture, the number should have been like 128MB or 512MB to not be a bottleneck. The choice of 32MB for the ESRAM optimizes the Xbox One for 720p 16bit resolution since its not enough for 1080p. The Xbox One also utilizes a similar AMD/ATI Radeon GPU but with 768 Shaders vs 1156.
Xbox One opted for 8GB 68.4 GB/s DDR3 (vs GDDR5) which took one of the major advantages of the PS4 unified system and made it a disadvantage. The Xbone GPU will also be gasping for RAM during graphical sprints.
This is a pretty big step back for the XBOX One, however, the Original XBOX 360 didn't have a HDD and had some other small issues like overheating. I would think Microsoft may upgrade the ESRAM or the DDR3 to GDDR5 in later versions. This would help increase minimum frame rate and make it easier for later games to run at 1080p.
In conclusion, I would have liked to see this generation run at 4k 60fps or upscale to them competently. All is not that bad though we do have computers which can run that and the introduction of the 8th gen systems means we all will benefit from DirectX 11 visuals which has long been held at bay by the least common denominator.
EDIT UPDATE: Sources from China have confirmed a "new" version of the XBOX ONE is in the works. What's not confirmed is what's different. Some have posited its the $349 version without a kinect but that doesn't seem to hold water as they would just ship the current version without a kinect. The new version is a new Xbox One with modifications to the hardware hence "new" not just "re-bundled". It is likely that this report confirms an Xbox One is in the works using GDDR5 to be built early next year.