After comparing Sakura's and KAA's 720p releases, and the screens posted above, this is what I've noted.
Sakura's...
• Retains less grain and fine detail than KAA (this is the case even with KAA's 720p vs. Sakura's 1080p), but more than Raws-4u and CalChi.
• Is antialiased.
• Cleans up the chroma bleeding around lines a bit.
So, out of the three comparison shots posted, Sakura's is the clear winner. CalChi's is way over-sharpened and Raws-4u retains less detail than Sakura's with none of the benefits of antialiasing or chroma cleanup.
Also, here's a comparison of
Sakura's 720p Spline36Resized to 1080p vs. the native 1080p shot that was posted. And here's a comparison of
KAA's 720p Spline36Resized to 1080p vs. Sakura's 1080p.
As you can see, KAA's retains more grain and fine detail, like I mentioned. More surprising, though, is that Sakura's 720p actually seems to retain more grain and detail than the 1080p. Which makes me think even more that there's no point in uploading a 1080p version at all.