Ultrawide cameras rarely do well in low-light video capture and that's truer on the Xiaomi here than on any of the others - it's dark and soft beyond what we'd call normal. The Huawei is also softer than average, but at least it's exposed well. The Oppo and the Galaxy are doing a decent job within this context, and the vivo is a little better, but not necessarily to a game-changing level.
Low-light video, ultrawide (0.6x): Huawei • Oppo • Samsung • vivo • Xiaomi
The Galaxy is somehow the best of the bunch at 23mm despite having the smallest sensor. Out of the one-inchers, the Xiaomi and the Oppo are a touch better than the Huawei, though not enough to be of any significance. The vivo is obviously not up to the task at this zoom level.
Low-light video, wide (1x): Huawei • Oppo • Samsung • vivo • Xiaomi
The vivo is unremarkable with tis main camera at its native 35mm, where the Galaxy is actually no worse despite having to zoom in a little. The others are noticeably softer.
Low-light video, standard (35mm): Huawei • Oppo • Samsung • vivo • Xiaomi
The Oppo sets the standard at 70mm, delivering clean and sharp results. The Xiaomi is pretty good too - about as sharp, but grainier. The Galaxy is noisier and softer but still decent. The Huawei is cleaner and sharper than the vivo, better than the Oppo, and properly good in isolation.
Low-light video, short tele (3.0-3.7x): Huawei • Oppo • Samsung • vivo • Xiaomi
Zooming in further, the Xiaomi and the Galaxy are alright at their respective long tele levels but we wouldn't say they're a match for the Huawei above (at 89mm or whatever Huawei calls it). We do think that the Xiaomi and the Galaxy have a bit of an edge over the Huawei and the vivo and their digital zoom to 135mm. The Oppo is also apparently not using its 6x camera here so it too isn't great at 135mm.
Low-light video, medium tele (4.3-6.0x): Huawei • Oppo • Samsung • vivo • Xiaomi
Going all the way to 10x, it's the Huawei that is giving us footage that's close to usable - the others are pretty hard to like.
Low-light video, long tele (10x): Huawei • Oppo • Samsung • vivo • Xiaomi
You can check out the playlist below, which includes all the video samples from which we grabbed the frames above.