Well, the higher the resolution the better it compresses, specially for the same amount of global detail.
That’s because pixel level artifacts and macroblocks become smaller in comparison 😃
With sound it’s the same, we use 48kHz and 32bit compression to reduce artifacts.
But the actual source material might only needs 32kHz and 12 bit in terms of actual detail.
I understand the reasoning behind using 720p for ANH and I agree for uncompressed images.
But for compressed videos, you need a higher resolution to keep all the 720p detail. And most people are likely to see highly compressed versions 😉
Here’s an interesting example with images (Higher resolution or lower compression JPG’s?):
Resolution always wins 😃