It seems since about 720p quality bottleneck is more in codec artefacts than in the resolution.
So for overall effects it would be probably better to give additional bandwidth to less lossy codec / settings than just to pure resolution (their first video "Life in the garden" has 28 MB in 720p and 91 MB in 4k resolution).
http://www.youtube.com/view_play_list?p=5BF9E09ECEC8F88F
It seems since about 720p quality bottleneck is more in codec artefacts than in the resolution.
So for overall effects it would be probably better to give additional bandwidth to less lossy codec / settings than just to pure resolution (their first video "Life in the garden" has 28 MB in 720p and 91 MB in 4k resolution).