None of these three phones here would've risked omitting 4K video recording - the 2160/30fps mode has been the norm in the top category for a while, not to mention it can already be found on more opportunistic midrangers too.
But here's where no other phone, midranger or flagship, can compete with the Xperia XZ Premium. The Sony smartphone can record video at up to 960 frames per second, albeit for a fraction of a second at a time (0.18s) and just in 720p resolution. We can't not open the video recording chapter with this one.
The G6 has a trick up its sleeve too - it's got a wide-angle camera that can cover a 125-degree FOV and is perfect for action videos, in 4K of course. Not much action in the sample below, though.
The regular 2160p footage produced by the phones differs somewhat, but they are all dependable as high-res camcorders. The level of captured detail is comparable, with the G6 perhaps having a minor edge in resolving the finest textures. The S8 is the most contrasty, with overall most pleasing colors. The G6 dials the saturation a bit high up, while the Xperia's video is natural without looking dull.
It's the Galaxy S8's 1080p footage that looks the best, with the Samsung phone capturing the most detail and doing so with mature processing. The G6 isn't as good at holding on to detail at the lower resolution and coupled with heavy sharpening this makes for a rather artificial look. The Xperia's rendition is again conservative and the footage is a bit soft.
This continues in the higher framerate 1080p/60fps, where the S8's superiority is even more evident. It's no 960fps, though.
In 4K, the G6 lacks electronic stabilization to go with its optically stabilized lens and it shows in its footage. The S8's digital stabilization is available in 4K alongside OIS. As for the XZ Premium, it allows you to select the 3-axis Standard variety of its SteadyShot stabilization (but not the gyro-assisted Intelligent Active mode). Both do a good job of stabilizing global movement, but depending on the use case, the S8 may exhibit a peculiar wobble (no we're not walking funny), while we experienced no such issue on the Xperia.
Switching the resolution to 1080p lets you enable the G6's stabilization, as well as bump the Xperia's stabilization to Intelligent Active. The Xperia's footage gets even smoother and is on par or in some instances better than the S8. The G6 isn't quite up to the same standard.
Winner: Tie. It's nearly impossible to pick one of the three - they're that good. The Xperia scores major points for its slo-mo video, but some will argue it's of limited use. Good thing then, that the Sony smartphone also excels in 4K and has a stabilization that works. The Galaxy S8 captures very good 4K itself, but reigns supreme in 1080p, where its stabilization also functions better than in 4K. The G6 has perhaps the most detailed 4K video, and with a wide-angle cam on top of the regular one it's a boon for action shooters.
In low light, the LG G6's metering opts for a darker exposure, thus sacrificing a some fine detail in the shadows, but arguably better preserves the vibe of this sunset scene. The Galaxy S8 went for the brightest exposure of the three and has little noise - and not at the expense of lost textures either. The Xperia is keeping up, retaining heaps of detail, though a bit more punch would have been nice - the video is starting to look dull compared to the others.
Winner: Tie. To each their own. The G6 is a bit dark, but it's probably the most expressive here. The S8's footage is pleasantly punchy out of the box, while the more laid-back Xperia could use a boost of contrast, but some will appreciate its natural look.
A trip to our Video compare tool is always a good idea, too. The crops on the thumbnails below may be telling, but for the full picture be sure to click on them.