Live is always better because you’re able to interact with those who attend.
The challenge is getting enough people to attend.
If the conversation feed is quiet, everyone will know that hardly anyone is there.
That could damage your credibility.
So if you’re sure that you won’t have at least a few hundred people who come to it live, then you probably ought to record it, and then make it available to those who sign up.
The one thing you must not do is tell people it’s live, but then deliver only a recorded version.
Doing that makes your stuff look dated; not evergreen.