There is a great deal of discussion over the ORAC comparison between Acai and Aronia.  USDA reported a Total ORAC value (Hydrophilic + Lipophillic Oxygen Radical Absorption Capacity) for Aronia of over 16,000 micromoles Trolox Equivalents per 100 grams of fruit.  Some websites suggest that Acai is significantly less.

See the attached USDA reports. USDA Food ORAC 2007; USDA Food ORAC 2010