They both go through an api layer (DirectX for Xbox, LibGCM for PS), but this layer is as thin as can be (low level) and they expose all the features of the system and you can also go "direct to metal" but it is generally not necessary unless you want to really fine tune performance. These console api are really light and low level that you can do whatever you want to do in that environment. Xbox 360 has a DirectX 9+ api layer in that it is similar to the one on pc but without the OS, drivers, system overhead, and all the features on the system was exposed. The DirectX 11.x layer on the durango is also similar to the one on PC but I would expect minimal overheads and it exposes all the custom features of the system.