I buy both, generally at launch. I didn't used to, but as I started to know fewer people with the games, I wanted to be able to trade with myself to get all of the version exclusives. Moreover, I like having multiple saves, and traditionally, that's required multiple cartridges (though perhaps not on Switch). In general, I started getting any game I want at launch (Pokémon and others) after waiting and having trouble finding physical copies a few too many times.
I still plan on getting both games for gen 8. I'm not quite sure what to about the profiles (maybe I should split the saves over two profiles in case I ever get a second Switch so I can trade with myself; not sure what that will mean for bank access though).