Comparison: iPhone X vs. Galaxy Note 8 video quality

The Note 8's optical image stabilization does a better job for walking, but this time the image is overexposed. Even though the stabilization is smoother, the Note consistently back-focused, or focused on objects behind the intended subject.

After repeated autofocus tests, the iPhone did a much better job with autofocus tracking, especially for close-ups. The Note 8 not only takes longer to focus, but also suffers from focus hunting, while the iPhone focuses almost instantly.
 

Taking a look at lowlight, the Note is aggressively de-noising, providing a more pleasing, but much less detailed image. Using the telephoto lens, the Note 8 has less noise, more detail, and better colors, beating the iPhone X in every way.
 

The iPhone's 4K 60 recording provides for smoother video, especially if you're going to slow it down. As you can see, the Note's 4K is unusable for slow motion because of the choppiness.

If you want smoother slow motion on the Note 8, you can also shoot at 60 frames per second, but you're limited to 1080p, which means overall quality takes a hit.

The iPhone X can shoot super-slow motion at 240 frames per second at 1080p, whereas the Note 8 can only do it at 720p. Overall, the Note 8's image had less detail, a lot more artifacts, and was consistently underexposed.

The Note 8 did take the lead in a few categories like low light and stabilization, but overall the iPhone X is definitely ahead with much faster and more accurate autofocus, more true to life colors and contrast, and in general more detailed video. It also the shoots much better super slow motion and is the only phone to support 4K at 60 frames per second, making it the a solid choice for mobile videographers.