We switched from chat (Slack) to forum (Vanilla) about a year ago and most members are quite happy about it (mainly about the better organization, search and available history). And although no one would want to switch back, we also hear that the move to the forum made some members feel more disconnected from the rest of the community.
Forum discussions tend to be quite a bit more formal compared to chat. Going to a forum is a more deliberate move since you need to actively go to the website, instead of getting notifications from your (Slack/Discord) chat app that you already have open. And probably