When I tested it locally, I found that the forum home page (forum.php) loaded approx. 33% faster with DBSEO compared to vBSEO.
This is not a test that I've repeated on this forum (we no longer have vBSEO installed), nor have anyone who switched reported any differences one way or the other - that's why we haven't made any hard claims regarding performance benefits of upgrading.
It really is a Your Mileage May Vary kind of situation, if I'm honest. What I will say is that we'll be taking further steps to improve the performance of DBSEO in future versions, by utilising the Datastore Caching functionality further on common operations.