Camera testing specialist DXO ran the new its results are in: the S6 has a better ability to resolve detail than the 's camera, and its video is as good or better in almost every way. Except image stabilization, that is, where they're both awful.'s camera through its battery of tests and
Given the specs of the two cameras, the photo results are unsurprising. Detail and artifacts both depend heavily on sensor size and resolution, and the S6 is bigger on both counts.
On the other hand, the iPhone fares better when it comes to artifacts, a category that seems to lump in everything that's wrong with a photo except noise. I suspect that's partly because the S6's native shooting mode has an aspect ratio of 16:9 ("normal" photo aspect ratio is 4:3 or 3:2) and its lens really distorts toward the edges of that wide angle of view.
Of course, there are tons of tradeoffs that I see between the two just by looking at the samples in. For instance, the S6 gets pale caucasian and olive skin tones better in daylight, but the iPhone does better under indoor lighting.
I wish the S6 supported Android 5's latest camera API; then we'd be able to shoot raw and really see what the camera is capable of.