Frankly, with multiple devices, the quality difference isn't as big an issue as it once was. IMO, you should use the system that's best suited for the environment.
To Alisa and I, it really depends on the motion needed and the number of Kinects devices used. We use both PS Eye and Kinect based systems here and, even though we mainly use multi-Kinect for our personal projects, we have also used the multi-Kinect system to create mocap for commercial film and TV productions. The usage was originally meant to be experimental but we wound up using the data for final production.
Generally speaking, data from two Kinects devices is comparable in quality to what you can get with four PS Eyes. This is because you're recording actual depth data as opposed to a 2D image with PS Eye. If you use three Kinect devices, the quality is better--but then the system begins to require more space. (We can just squeeze in 3 kinects in our home studio and still have about 6 x 7 feet of performance space.)
The biggest difference will be in the ability to capture fast motion but 'fast' depends on what you mean by fast motion. For some of the film work Alisa and I did last year, iPi Mocap Studio was mainly used to add motion to digital stunt doubles. In one film, we needed fast motions for actors that were falling from a great height, and Mocap Studio using only two Kinects captured the flailing motions very accurately. (I'll see if I can post some of these shots along with capture video.)
Of course, if what you mean by 'fast motion' is a lot of running and jumping, you're not going to be doing that in a small room anyway. If that was what we needed, then we probably would have used PS Eye at the soundstage where I used to work--but now we're talking a fairly huge space again. (Alisa and I may have both systems at home but the movie studio where I worked last year had the PS Eye system, and even they were considering getting the Kinect setup for its quick setup convenience after they saw the data I was bringing in from home using the dual and triple Kinect system.)
As for the frame rate difference, 60 fps does give you greater fidelty over 30 fps, but you also need to factor in that Kinect is not just 30 fps, it's also recording three dimensional volume which the PS Eye does not. Once you start adding multiple Kinect devices, the difference in fidelty becomes less noticeable. (That said, for really fast motion, yes...higher frame rate is still much better.)
BTW, having a small space does not necessarily limit the size of what you're mocap represents. In the example, mentioned above, the characters in the move were supposed to be falling hundreds of feet. In another film, a giant creature was walking for hundreds of yards, and in yet another film, I used to to make an actor appear to be leaping across a wide chasm (much wider than our living room.) The trick is that you can manipulate the data in all sorts of interesting ways once you get it out of Mocap Studio and into your 3D animation system. (Some of 1KO's early iPi examples illustrated this brilliantly.)
Here is a very old example of a fast motion from about three years ago using two Kinects when Kinect support was still an experimental feature in iPi Desktop Motion Capture version 1. This was meant to be a height test because Mocap Studio was not normally used to record small children, but I was surprised that it captured my five year old daughter's quick motions fairly accurately:
Mocap Test with Small ChildKeep in mind, accuracy was not the intention in this test--at the time, we were only interested to see if the system could capture a child's motion at all, but even with the experimental version and only two Kinect devices, it capture fast motions surprisingly well.
Nowadays, with the improved version 3 software and possibility of up to four Kinect 2 devices, I think the data would be far better that what I was capturing with only two devices three years ago. And in a small room like this, I would say the data is better than PS Eye, especially since you would not be able to get enough Eye cameras set up in this space with proper lighting anyway.
Hope this helps.
G.
P.S., man, I really need to get some new examples posted online--it's been a couple of years since I posted anything new. I'll see if I can get permission to post work from some of the feature films Alisa and I worked in 2013-2014 which used iPi Mocap System. These days my daily work is mostly in 2D cartoon production for Dreamworks Animation but I still use iPi Mocap for my personal 3D productions at home--I'll try to make time to post some of my recent personal stuff too.
