In ideal light, and when using automatic settings, both the Galaxy S9 Plus and the iPhone X are at the top of their class in terms of mobile photography. This is shot of the lake looks brighter with the Plus.
While the iPhone's version has more contrast and texture.
You'll notice slight differences in color temperature and texture in general landscape shots. The Galaxy S9 Plus tends to be a warmer...
...While the iPhone X has cooler hues.
In this shot of Samuel in the snow, it's the S9 that has the higher contrast.
And the same shot of on the iPhone X looks brighter, able to pick up more of the highlights in the snow.
But in this shot of the lake and the trees, the contrast on the Galaxy S9 Plus looks subdued in comparison.
This shot on the iPhone X has higher contrast and looks sharper.
Both the Galaxy S9 and S9 Plus have a variable aperture on the main, wide-angle lens which allows the lens to adjust to changes in light. This photo was taken with the narrow f/2.4 aperture.
While this one was taken with the wider f/1.5 aperture to make it look lighter.
This is the same shot on the iPhone X which has a fixed aperture of f/1.8.
Like the iPhone X, the Galaxy S9 Plus has a second 12-megapixel telephoto lens for optical zoom at 2x magnification.
Here's the same shot at 2x zoom.
This is the iPhone X's version from the wide-angle lens.
And here it is using the telephoto lens at 2x zoom. At 2x magnification, both produce great results. However when I looked closely at the shots, I noticed the S9's was a bit sharper.
The phones also also use the second telephoto lens to create blurred background effect on portraits. On the Galaxy S9 Plus, it's called "Live Focus".
And on the iPhone it can be found under Portrait Mode.
Portraits on the S9 appear to be more flattering because it makes faces brighter and evens out shadows and skin tones.
While portraits on the iPhone seem to be cooler and more true to life, because is retains more details in the faces of people, babies and dogs (which is what I tried it on).
But sometimes the retouching on the S9 Plus can backfire. In the photo above, the S9 seems to have applied the same filter on my face as it did to my son. On his face it evened out his skin tone and reduced redness, but the same effect on me made my skin turn yellowish.
The iPhone's shot may not be perfect, but it's closer to what we actually looked like in the cold.
In this shot you can see how the S9 Plus even applied a whitening filter to the pup's fur.
The dog's fur looks more natural here, but he's out of focus.
And if you're a fan of selfies, both phones also have a blurred background effect on the front-facing cameras. The S9 Plus has a slightly sharper 8-megapixel sensor with a wider angle.
While the iPhone X has a 7-megapixel depth-sensing camera which is slightly better at figuring out what to blur in the shot. But both rely on software to create the portrait effect, so neither is as good as the rear-camera. In other words, don't expect perfection.
Food shots are impressive on the S9 Plus, even in this dimly-lit restaurant. Just look at the texture it was able to capture on the green onion.
The same shot on the iPhone looks darker and not as sharp.
When the subject is standing still, like this shot of Charlie the pup, the Galaxy S9 has no problem. The shot looks bright and sharp, but it has an orange glow.
The shot on the iPhone X looks dark and grainy in comparison, but colors are more accurate.
You'll notice the same orange glow on this shot of the S9 Plus, and low-light shots when the subject is moving aren't as sharp.
The iPhone's color temperature seems more true to life, but the shot looks darker.
But here's where the wider aperture on the S9 Plus really helps. In this shot of the lake it let in more light without sacrificing detail and picture quality.
There's a lot more noise in this shot of the iPhone X and you lose detail in the lights on the horizon.
The Galaxy also did a better job at evening out the lighting in the cabin shot above.
In this picture the cabin looks blown out.
The S9 Plus is the clear winner in low-light photography and it has a much wider range of results because of the variable aperture and manual settings.
But the iPhone X produces consistent results, colors seem slightly more accurate and portraits more true to life.