ArangoDB is OrientDB done right, but it's a lot younger.
If you're considering using either, you owe it to yourself to investigate whether postgres's Common Table Expressions [0] can do what you want instead. If you can stick with something more mature like postgres, then you'll be saving yourself a lot of pain.
[0] http://www.postgresql.org/docs/9.1/static/queries-with.html
How are you backing this ? I am sure Luca from OrientDB will have some comments.
@lvca, I find your comment distasteful and it's not the first time I see you trying to shutdown people who criticise OrientDB (https://news.ycombinator.com/item?id=9253488) when you should really be thanking them for exposing the issues they face (a lot of people don't go public). It would be more productive to engage @phpnode, @anonwarnings and others, listen to them, raise issues in the bug tracker and address them. Accusing people of trolling or flaming doesn't benefit OrientDB or its users at all...
Unfortunately I haven't tried ArangoDB so I can't make any comparisons with OrientDB but I hope both succeed!
What is your opinion about OrientDB community ?