pretty much what you said is i. I can't think of anything else other than emails are like mail IRL so each one is self contained which is basically a rewording of what you already said. 🤣
chats are throw-away little snippets of conversation and not really conducive to long writing, I'd add. personally I always set them to auto delete in a week.
(I like having both of these ways because they both have a purpose and appropriate uses based on what is being discussed. I also don't really want my email mixed with Nostr because I'd rather not have everything in one system.)