I'd have to narrow it down between Aldon Smith and Justin Smith. Justin Smith has the ability to push the pocket and collapse it to a degree in which holes open up clean up duty for our inside backers. He can also hold up multiple "blockers" which sometimes isn't necessarily a good thing. Aldon on the other hand, has tremendous athletic ability to bull rush while at the same time setting the edge. That can give time for the line to "slide" while maintaining a great edge.
It's a tough call. I think Justin comes out on top.