Tough decision! Farenga is a popular speaker and I'm sure he has a lot to say. He coauthored a book on home education; I think it was "Teach Your Own". I'd probably go to see him, unless I had a specific reason to attend the conference. The state level stuff can be a bit elementary and "plain vanilla" in tone, though there may be a session or two that caters to parents and teachers of HG plus. Big conferences may give you some perspective though, on how "out there" your own gifties are, and maybe give you a chance to connect with other parents and kids.

Looks like you'll have a good day either way! Have fun!