Nexus 6P RAW vs JPG*
* Actually Custom vs In-Camera Processing

Although this is a comparison of RAW vs JPG, it's not about the file format. The comparison is really External vs In-Camera image processing:

JPG files from your phone's camera are always processed by the the camera's firmware before being saved. This processing severely degrades the image.

RAW files completely bypass being processed by the camera's firmware, and are a direct representation of what hit the camera's sensor. This means any app can replace the processing normally done in your camera.

So, the "JPG" column isn't really showing how bad JPG is. It's showing you how bad the phone's camera firmware is. It consistently ruins the image in two ways:
RAW Developed in Lightroom 6.0 (Luminance Noise Reduction OFF, Chroma Noise Reduction 25%)
View mode: Side-by-Side
Switch to A/B Toggle
JPG
In-Camera Processing
RAW
Lightroom Processing

Outdoors Dusk IV (81 ISO) - JPG 100% Crop

Outdoors Dusk IV (81 ISO) - RAW 100% Crop
This RAW reveals just how much detail the 6P captures before being smudged by default processing. Subtle blue tones in the leaf, cracking, and fine veins all show through very well. Even more impressive is that this crop is from the edge of the frame, where resolution typically falls short.

Daytime (60 ISO) - JPG 100% Crop

Daytime (60 ISO) - RAW 100% Crop
Again, the RAW contains far more detail than I would have ever expected from a phone. The built-in processing (left) completely mangles the image and destroys all of that detail. I'm beginning to feel really bad for camera engineers who work on phones -- they build a device that punches way above its weight, only to have it all destroyed by the in-camera software.

Cloudy II (85 ISO) - JPG 100% Crop

Cloudy II (85 ISO) - RAW 100% Crop
Complete garbage on the left: the trees in the background have become a mush. Their red-brown leaves are muddy gray. The backhoe's yellow-orange is muddy gray. I don't understand why noise reduction is even used here! The RAW noise level is already low.

Lime (198 ISO) - JPG 100% Crop

Lime (198 ISO) - RAW 100% Crop
A 100% crop of a lime. These don't even look like they were taken with the same camera.

Cactus Flower (67 ISO) - JPG 100% Crop

Cactus Flower (67 ISO) - RAW 100% Crop
A very small (~5mm or 1/4") flower. The texture of the leaves is completely different on the left.

Cat. (243 ISO) - JPG 100% Crop

Cat. (243 ISO) - RAW 100% Crop
Right: Cat; Left: Worse cat.

Bricks (660 ISO) - JPG 100% Crop

Bricks (660 ISO) - RAW 100% Crop
The default noise reduction algorithm has no idea what to think of bricks.

Office wall, spotlight. (144 ISO) - JPG 100% Crop

Office wall, spotlight. (144 ISO) - RAW 100% Crop
The image on the left has completely blown out highlights, total loss of details in the bright areas, and strong blotching / oversharpening in the background.

Cameras (167 ISO) - JPG 100% Crop

Cameras (167 ISO) - RAW 100% Crop
On the left: big changes to metallic surfaces; the out-of-focus areas are oversharpened. Everything is oversharpened.

Sand Toy (60 ISO) - JPG 100% Crop

Sand Toy (60 ISO) - RAW 100% Crop
A macro shot of this sand toy shows built-in noise removal annihilating sparkly bits of sand.

Cloudy (60 ISO) - JPG 100% Crop

Cloudy (60 ISO) - RAW 100% Crop
Low-contrast outdoor scene.

Outdoors Dusk (60 ISO) - JPG 100% Crop

Outdoors Dusk (60 ISO) - RAW 100% Crop
More of the same.

Outdoors Dusk II (69 ISO) - JPG 100% Crop

Outdoors Dusk II (69 ISO) - RAW 100% Crop
The default processing (left) tends to make everything look like watercolor. Hopefully everybody prefers that to actual detail.

Outdoors Dusk III (85 ISO) - JPG 100% Crop

Outdoors Dusk III (85 ISO) - RAW 100% Crop
While the default JPG seems to completely ruin colors of overexposed areas (yellows), these colors are well preserved in the RAW file.

Cloudy II Overexposed (Uncorrected) (85 ISO) - JPG 100% Crop

Cloudy II Overexposed (Uncorrected) (85 ISO) - RAW 100% Crop
There appears to be aggressive highlight clipping in the default JPG's clouds, but not in the RAW file. Below we'll see if that's true by reducing the exposure 4x (or -2 EV).

Cloudy II Overexposed (-2 EV) (85 ISO) - JPG 100% Crop

Cloudy II Overexposed (-2 EV) (85 ISO) - RAW 100% Crop
Reducing the exposure by 4x shows that the RAW contains far more dynamic range than the default JPG, which harshly clipped the bright areas in the clouds, destroying detail.

Indoors, Average Lighting (100 ISO) - JPG 100% Crop (Nexus 5X)

Indoors, Average Lighting (100 ISO) - RAW 100% Crop (Nexus 5X)
An indoor shot of average brightness. The default JPG has applied aggressive noise reduction and then sharpened everything, resulting in smudges with halos. The greens in the plant are gone, too.

Mostly Darkness (1348 ISO) - JPG 50% Crop

Mostly Darkness (1348 ISO) - RAW 50% Crop
A very dark outdoor shot at a moderately high ISO. While the RAW file appears very noisy, it still contains far more detail than the default JPG. Does anybody prefer the image on the left? Why is the default processing so afraid of noise?

Mostly Darkness II (1348 ISO) - JPG 100% Crop

Mostly Darkness II (1348 ISO) - RAW 100% Crop
Same situation as above. The RAW contains more noise, but also contains more detail, color, and intensity range. We can easily see the vague tree line against the night sky.

Mostly Darkness III (1088 ISO) - JPG 17% Crop

Mostly Darkness III (1088 ISO) - RAW 17% Crop
Even across the whole image, RAW files look better. This is scaled down to 17% of its original size, but the RAW file still shows better color, more detail in the shadows, and no 'crunchy' watercolor effect. It does start to show some strong blue tinting in the shadows, though.

Very Dark Indoors, Overexposed (1892 ISO) - JPG 67% Crop

Very Dark Indoors, Overexposed (1892 ISO) - RAW 67% Crop
Very dark indoor scene of a dim (~25W) light, overexposed. They're both pretty bad, but the default in-camera processing wanted every detail in the JPG to die.

Medium-Lit Indoors (60 ISO) - JPG 100% Crop

Medium-Lit Indoors (60 ISO) - RAW 100% Crop
Some potted plants against a dark window. In-camera processing seems to really hate leaves. It also made the pots look like playdough. Cool?

Overexposure Correction (Uncorrected) (494 ISO) - JPG 33% Crop

Overexposure Correction (Uncorrected) (494 ISO) - RAW 33% Crop
Indoor shot slightly overexposed. Pay attention to the color of the wood on the cabinet, and the intensity gradient on the bottom white thing (convection oven). The next image lowers the exposure 8x (-3 EV)

Overexposure Correction (-3 EV) (494 ISO) - JPG 33% Crop

Overexposure Correction (-3 EV) (494 ISO) - RAW 33% Crop
With an 8x (-3 EV) lower exposure, the color of the cabinet's wood grain stays true in the RAW, but turns a strange yellow-green in the default JPG. The bottom white thing also shows stronger highlight clipping.

Overexposure Correction II (-3 EV) (494 ISO) - JPG 40% Crop

Overexposure Correction II (-3 EV) (494 ISO) - RAW 40% Crop
Same image, different place, again with the exposure reduced 8x (-3 EV). The default JPG's oven mitts have completely clipped to white, and we get no more detail out of the countertop's texture. Although the RAW file gives us some room in the highlights, it's not very pleasant ... but I'll take it.

Underexposure Correction (Uncorrected) (1348 ISO) - JPG 30% Crop

Underexposure Correction (Uncorrected) (1348 ISO) - RAW 30% Crop
A severely underexposed outdoor night image at moderately high ISO. The RAW file shows more noise as usual (who cares?), but also shows more detail. Let's see what we can get if we adjust the exposure up by 4x (+2 EV) below.

Underexposure Correction (+2 EV) (1348 ISO) - JPG 30% Crop

Underexposure Correction (+2 EV) (1348 ISO) - RAW 30% Crop
Increasing the exposure 4x (+2 EV): ouch. There is absolutely no more detail to be had in the shadows of the default JPG. Although the RAW file looks unusably noisy, it manages to reveal detail that wasn't visible before. The garage door's windows are much more clear, the strip along the roof is well defined, etc. You can actually identify the roof shingles.

Extreme Darkness (3762 ISO) - JPG 100% Crop

Extreme Darkness (3762 ISO) - RAW 100% Crop
An extremely high ISO night shot in near total darkness. Some 'real' cameras even struggle with noise at more than 3200 ISO. The RAW is ridiculously noisy, but does anyone really prefer the default JPG's smudges? One looks like film grain, the other looks like a disaster.