High resolution capture is beneficial even when the output resolution is reduced. Advantages include better image quality, but also extend to less familiar areas including creative flexibility, post-production, prints and future-proofing. This article summarizes how each of these aspects is influenced.
Better resolution has been a primary goal of technological advances in consumer video and cinema over the past several decades - from VHS to DVD to Blu-ray. With the recent push toward even higher resolution displays, such as Apple's Retina devices, this trend is expected to continue. In those situations, higher resolution is clearly beneficial for detail and realism.
On the other hand, resolution also has other lesser known benefits - many of which apply even when the output resolution is reduced. A common workflow with television has been to capture at 4K or higher, but to downsize this for 1080P display. One's initial reaction might be to think that all the original resolution has been wasted, and that one could achieve an equivalent result by just capturing at 1080P in the first place. However, as the examples in this article will demonstrate, that initial reaction would be a mistake.
See full details and examples of Motion Capture at 4K on the RED 101 Article: MOTION CAPTURE AT 4K AND BEYOND