It really depends on how much space you have to work in, the quality of the lighting, and how much effort you want to put into the capture/tracking process.
If you don't have a lot of space, like me, I really like dual Kinect. It's as accurate as using four PS Eye cameras. The trade off is that you don't have nearly as large capture space (which we don't have in our home studio anyway.) Dual Kinect is also easier to calibrate and doesn't require special clothing or lighting requirements. (Well, technically speaking, it requires different lighting requriements but it's still easier to deal with.)
Four PS3 Eye cameras are probably better if you have more space and if need to capture very fast motion. Two Kinect works fine for many motions though, even some quick ones. Four PS3 Eye cameras are also less likely to have occlusion issues, but you can work around most of these issues using dual Kinect as this test video of my daughter when she was five illustrates:
Mocap Test with Small Child (1 meter tall)If you go with four PS3 Eye cameras, be sure you have appropriate lighting. This configuration requires that the subject be lit fairly evenly with no hard shadows. When I was using the system, I used two - three soft boxes to light the stage. That's probably overkill but the point is, the system works better if you can control the lighting situation.
Kinect doesn't require even lighting but it's can be affected by IR interference from other sources like natural sunlight. In this case, you need to be able to cover your windows or do all you capture at night.
If you decide to go with Kinect, I highly recommend Kinect for Windows over the 360 version. Both types are becoming hard to find though because the original Kinect has been discontinued. It's much easier to find Kinect 2 nowadays but, as you may know, you will need a separate computer for each Kinect 2 device.
Hope this helps.
G.
