there are predictions that distinguish between MWI and Copenhagen.
I don't believe that he said anything of the sort. At about 50min Scott talks about quantum speedup as utilizing the computational power of many worlds, provided they exist, not as any kind of experimental distinction (indeed, quantum computing is interpretation-agnostic).
I was talking about the blog post, not the bloggingheads video. He doesn't outright declare that the two interpretations are distinguishable, but that position is strongly suggested by both his discussion of betting on the extension of linearity to macroscopic scales and his subsequent discussion of the Wigner's friend experiment.
http://www.scottaaronson.com/blog/?p=1103
Eliezer's gung-ho attitude about the realism of the Many Worlds Interpretation always rubbed me the wrong way, especially in the podcast between both him and Scott (around 8:43 in http://bloggingheads.tv/videos/2220). I've seen a similar sentiment expressed before about the MWI sequences. And I say that still believing it to be the most seemingly correct of the available interpretations.
I feel Scott's post does an excellent job grounding it as a possibly correct, and in-principle falsifiable interpretation.