There are lots of reasons why game developers and related people are considering the PS4 a nearly perfect gaming PC.
- It uses PC stuff, which implies that lot of tools and experience are available to the console, instead re-inventing the wheel.
- The console hardware is fixed. Therefore developers can target the same metal.
- The OS allows for coding at low level, maximizing the usage of resources.
- No incompatibility from old drivers and/or different updates.
- Innovative hardware never seen in a PC before: APU-HSA, hUMA, fast GDDR5 as main memory...
Regarding performance the PS4 will be a beast. Epic showed a demo at GDC 2013 where the PS4(*) was able to compete with an ivy bridge i7 + 16 GB RAM + GTX-680. It was behind this high-end gaming PC by only a fraction of the price!!!
(*) The funny part is on the details:
The developers received the kits weeks before and had no time for tuning the demo beyond a fast port from the PC, therefore the demo run without any optimization.
They also used an early API, unlike the PC version which run on mature Windows API.
The demo did not run on final PS4 hardware but on an dev. kit with constraints. Developers only could use 1.5 GB VRAM and the full demo run only at 27-29% of the PS4 final specs!!!
Therefore the PS4 is faster than any available gaming PC.
Of course in some years things will change but then will become a PS5...