I personally think the notch is too large for such a small phone like the 12 mini. Takes up too much space along the top.
Also the SE display isn't much smaller. The SE's display is 16:9 aspect ratio (wider & shorter) and the Mini is 19.5:9 (thinner & taller) meaning the the SE has as much display area as a 5" 19.5:9 phone would.
Also the SE display isn't much smaller. The SE's display is 16:9 aspect ratio (wider & shorter) and the Mini is 19.5:9 (thinner & taller) meaning the the SE has as much display area as a 5" 19.5:9 phone would.