I finally got round to making a comparison test video of 4 good native 4K 'budget' action cameras. Budget in as much as cheaper than GoPro; ThiEYE t5e and Firefly S8, which both performed well, are sub £80 on promotion at the moment. The other two are closer to £170 and £200+ (Links on the videos.) There are two versions of the video, one VERY long, with 1080 60 and 4K clips but rendered at 1080 60 fps. And the other just has the 4K test clips but is rendered at 4K. There's a link to the short one in comments and on the video. Xiaomi yi2 was marginally the best. Best EIS (gyro stabilisation) Longest battery life and slightly better video quality, but 3 times the price of the lowest priced!