Ryu is much faster and more durable, that video with the exploding mountain top convinced me of that withotu doubt, and Dante's healing factor seems to be able to be worn down over tiem, even the DMC wiki, which is maintained by the DMC fanboys, seems to suggest this. but it IS a wiki, lol.
I think the main thing stoppinf Ryu from wining is the perception of Dante as unkillable. He IS killable, just not easily killed.
Dante cannot be decapitated. In DMC 3 we see a blade pass through either him or Vergil(can't remember which one) completely, an attack that would have bisected anyone else, and his healing was so fast that the part of the wound were the blade entered his flesh was fully healed before the sword was halfway through his body. Trying to decapitate Dante is like trying to cut liquid in half.