I wondered about the differences between Grape Seed Extract & Resveratrol, found this on a quick search.. might be a newer comparison somewhere.

[So, you may be wondering: What’s the difference between resveratrol and grape seed extract? One of the biggest differences is the concentration at which the two compounds act in the human body. Grape-seed-derived polyphenolic compounds are able to reach the brain in nanomolar concentrations, much lower than that required for resveratrol, which, according to Pasinetti, “allows for the development of therapeutic applications.”
] (2012 article)
http://www.asbmb.org/asbmbtoday/asbm....aspx?id=17684