I've tested the mijia mini and some other action cameras against dashcams. The action cameras typically have wider angle and smaller aperture lenses than the dashcams - great for a helmet cam but not so good for capturing details of moving cars. They still do a good job though if they can use the advantage of their higher video resolution than most dashcams.
Anyway, thanks for putting this together as I know it takes a long time to compile these comparison videos. As you said, there's not much between them. Personally I prefer the narrower FOV of the Mijia which is one reason why I bought it.