I've used both. Titan is not anywhere near production ready. And now it seems like they won't ever be. It's not even a real database. It's a library. You can't even delete indexes once you create them. I don't get why anyone would go with them. (Is this still the case or did they resolve that index issue?) Either way, OrientDB is more mature/stable and was much faster than Titan. Then, OrientDB is a multi-model, so it just has so much more capabilities compared to just a graph database. IMHO, Titan seemed like a toy in comparison.