Both are going to provide enough detail for a decent face, unless you want extreme closeups in game (if your head only fills 1/4 the height of a 1080p screen, you won't need a 1024x1024 texture or 1080p capture for it). The one that captures the best image would be the one I'd prefer. eg. Better lens quality, resolving power, contrast, colour accuracy and range, and low light performance - just as I prefer in my digital cameras over pure megapixel count!That should be an easy Kinect win. It's RGB camera has far superior resolution to either of the PS Eye's.
Kinect should be able to do an awesome 3D recreation though, so it captures your head shape. PS4 would have to do a lot more work for that and I'd guess wouldn't be as fast or accurate. the Kinect 2 avatar stuff was very cool, and I presume MS make available some SDK stuff for that, supplying biometrics that games can use.