The leaves are similar the fruit is similar but they are definitely different. Earlier this year I posted a pic of the Petite negra brebas and the neck on those is very long. In contrast, VDB breba just looks basically like a larger VDB main crop, much shorter neck. VDB main crop is consistently larger than PN too. Hopefully you will be able to judge for yourself in a few short weeks. My guess is if dna testing was performed they would be closely related. Both are very good trees.