Consider a conspiratorial interpretation of quantum mechanics according to which the universe is genuinely local and deterministic, but the initial conditions of the universe are jerry-rigged so that all measurements made by sentient creatures fit quantum statistics (even though events in general do not). This theory is empirically equivalent to many worlds. It seems clear that there are several senses in which it is not equivalent to many worlds. And I think there is good reason to assign it substantially lower prior probability than many worlds, since one would need to specify the entire initial condition of the universe in order to predict correlations that many worlds predicts based simply on Schrodinger's equation.