As I say, it is more obvious on the Mini 6. It especially affects those who want use the Mini 6 primarily in portrait. It bothers some people greatly, and others not, so need to try yourself if you have not done so already.
If you are happy with the Mini 2, that is great. The Mini 6 screen really is only very slightly larger.
I was starting to get frustrated with my Mini 2, as it is often stuttering, some apps would crash, and is stuck on iOS 12 (which is OK, but I prefer all my devices on the same version for a consistent experience).