I'm trying to comprehend how this is a dilemma... Science supposedly teaches that for any two theories that explain the same data, the simplest one is correct. Bayes can't talk about explaining data without invoking the science that collected the data... Can he?

It would seem that the theory of science includes Bayesian theory.

On the other hand, the practice of science requires either exhibiting evidence for theories or testing falsifiable theories. Many Worlds can trivially be falsified by actually finding a collapse, while its main distinguishing feature cannot be directly demonstrated. Thus, science focuses on searching for a collapse.

So... I still don't see the contradiction.

I also have to speak up in favor of metaphysics -- one poster claimed he'd take Science over Metaphysics anytime. Does he realize that that statement is itself metaphysical? Science cannot determine whether Science has priority over other things, and metaphysics by definition has priority over physics.