[MediaPi]

BTW: Try playing any 10bit HEVC video files on the RPi3 and tell me how far you get.

Try playing 3D MKVs or 3D ISO with fullframe content (MVC) on the C2 and tell me how far you get.

3d is a dead technology for home entertainment, not sure which manufactures are left that make 3d tvs anymore. No tv means no content produced for it.
whereas 4k hevc is right now and the future. do the maths, C2 is basically Rpi4, its the next iteration of these micro boards for kodi imho.

The reason why Rpi3 will remain the number one platform for kodi is because of price and ease of purchase. There is a big market for pirated addons (possibly the biggest for kodi) which don't need hevc or 4k or anything fancy, since the content isn't using those standards, (though if you start to torrent (which this market is to lazy for) you can download good hevc content?) that market will buy the cheapest and not notice the difference.

anyway back to point, if your buying a new board right now and want to keep that board for more than a few years, C2 is the better option. If you already got a RPi3 and not in a rush to get into hevc or 4k then wait, theres always new boards out every year and they getting cheaper.