I voted for Dragon Frontiers and Delta Species as tied for best set. The pokemon in DF are simply better, but while DF has some very good trainers it's missing the most important Trainer currently in the format. Delta Species has that Trainer (Holon Transciever) along with most of the Holon Engine exclusive to this set. Dragonite, Metagross, the Holon's energy Pokemon, and more than playable basic and stage 1's make up for the fact that there are only 3 Ex's in the set. If DS had more Ex's or if DF had Holon Transciever it would be a clear cut best set, but they don't so I have to leave them as tied.