Madison has better beaches, better youth sports facilities, and a brand new elementary school and community center in the works. Guilford has a new high school and better shopping and more restaurants/commerce. When I say “better” it’s not by much. They are very similar towns, and you won’t go wrong with one over the other. I would recommend walking around each down town and visiting the beaches (go to the Surf Club and Jacob’s beach) to see what feels best to you.