As part of an extensive performance comparison of Graph vs Relational DBMS, a colleague and I have published a detailed report of the discoveries found. The test, together with acquired results, can be found on the GitHub page below, compares Neo4J, SQLGraph and Vertica with respect to various query domains (such as large joins and neighbour traversal) as well as a varying range of data set sizes.

We have open sourced the implementation on github (link here) as we hope that this in turn will churn up interesting discussion!

Ps. Unsure if this is the right sub to post under, but it seemed the most appropriate!