I wish I still had my first-gen SE, because it actually fit in my small hands, and its nice solid rectangular body made it easy to hold and hard to drop. The home button on that unit was starting to give out after 4 years of heavy service and I didn't want to spend the money for an out-of-warranty repair.

Unfortunately the Gen 2 is also mostly "non-repairable"; I had to get a total phone replacement for something as simple as a dying Thunderbolt port. According to the person at the Genius Bar, the 12 Mini is much more repairable, more like the first-gen SE in terms of its internals.

This SE Gen 3 still has the rounded/slim iPhone 6 body style, so I would expect it to be equally non-repairable. So all things equal, I would still go for the 12 Mini over the SE Gen 2 if I could make the choice over again.