I didn't compare it, since I haven't used Gephi, but I heard it's useful for large graphs. I don't like the user interface. It looks a bit outdated. I guess it's a good visualization tool, but I am not sure what it offers regarding the data import options and storage. If I need data persistency, I would rather choose a graph database which offers visualization tool. But if I only want to visualize my data, I would probably turn to tools such as Gephi.