I think one advantage to meeting in person is that it humanizes the parties. Sometimes we (and I’ll admit to the same) tend to get a little too pointed or critical or teasing with our online communications and forget that there’s a human being at the other end.
Still, keeping things objective and impersonal may result in free and frank discussions but also sometimes - hurt feelings or online arguments.
I remember one time I was exchanging a bunch of emails with a British guy over some business deal and it ended up getting a little heated. Then he wrote something about how “emails can appear so cross” and suggested getting on the phone, after which we resolved everything nicely without further issue.
As far as the domain business though - I’m not selling to other domainers so I’m not sure how it would affect my actual domain business one way or another to meet fellow domainers. As far as I know, I’m selling to end users.