After taking the time to look at several apps side by side on the Mini 5 and Mini 6, for now, I think a lot depends on user preference for the various features. Maybe some things will be larger on screen on the Mini 6 once apps are optimized for the screen but there wasn’t all that much difference in the few comparisons I made.
The lighting is awful, both Minis have matte screen protectors on them, and I took the photos with my iPP 11 2021. This is mainly to compare size of information on the screen.
iBooks, sample from a Procreate book.

PDF of a SAS programming book. There’s more on the page on the Mini 6, but most of the extra isn’t useful info.

Procreate:

Spartan Camera Mangement app, landscape (slightly more on the Mini 5, but seeing the next camera’s name isn’t really useful):

Spartan Camera Management app, portrait (one more camera’s photos displayed on the Mini 6 but either is much better when compared to using the app on a phone):

The lighting is awful, both Minis have matte screen protectors on them, and I took the photos with my iPP 11 2021. This is mainly to compare size of information on the screen.
iBooks, sample from a Procreate book.

PDF of a SAS programming book. There’s more on the page on the Mini 6, but most of the extra isn’t useful info.

Procreate:

Spartan Camera Mangement app, landscape (slightly more on the Mini 5, but seeing the next camera’s name isn’t really useful):

Spartan Camera Management app, portrait (one more camera’s photos displayed on the Mini 6 but either is much better when compared to using the app on a phone):
