Hmm.. Anakin was capable of holding up to an early Jacen and slaying voxyn, whereas Ben actually held the edge over Gavar Khai when he centered himself, and also defeated two or so Sith warriors on Dromund Kaas' nexus, which are pretty good showings. He's also slain Lost Tribe Sith members in two seconds (on average, at least).
Anakin supposedly possesses immense Force potential and he has some pretty nice Force feats. Ben has solid showings with the Force as well but he has never displayed as much natural affinity or potential for the Force as Anakin. So I'd probably give the win to Anakin.
EDIT: Anakin also slew waves of Vong with a combination of lightsaber attacks and some stream of white light which is either Force Lightning or Electric Judgment, but that was in his moment of sacrifice and he tapped into Oneness.