I like the exports that Day One does if you’ve ever used that journaling app before (they do multiple kinds of exports). JSON, for if I need to write a script to import the data somewhere else. TXT for something nice and human readable. CSV for whoever wants to use this format lol. They also got a pdf printout just to make things look pretty. As for imports, I think they have import options for their competitor’s export options, but I’ve only used this once and I don’t remember the option I used.
But if it came down to just one, I’d say JSON is the most important for me. The other ones are just nice to have but not critical.
And np, I didn’t want you thinking everyone thought it was too expensive.
I try to find cross platform options for any software. I moved from Android to iOS a few years ago and always think I may move back so it’s nice to keep options open. That being said though, the apple ecosystem works so well with everything within it I sometimes double pay for services just to also have the convenience that comes with the ecosystem.