To be sure, if a theory does make unexpected claims that bear out, a strong case has been made that the theory has greater epistemological merit than antecedent theories.However, I claim that two theories with the same empirical confirmation are prima facie equally valid. There is no reason to suppose that whether one has been propounded before the other has any bearing on epistemological utility (and I hold that that utility is all that can be demanded of a theory beyond empirical agreement)
What about Einstein's/Dirac's claim that theories should be 'beautiful'? How does symmetry play a role as a deciding factor in theory selection?
Beyond Occam however, we can evaluate the imperative qualities of a theory - those that educe a sense of understanding. The primary modern demand for imperative-ness is deductive reasoning. Inductive reasoning is what we rely on in the empirical conformation/refutation process and spurs us to demand unexpected predictions. However, it is only through deductive reasoning from grounded axioms that we can be sure of a theory's truthfulness.
I don't think any theory is purely deductive in its origin or purely inductive in its origin. If that's correct, it becomes a matter of deciding whether a theory is more 'true' because it is more deductive than the other theory. The problem with this view is that over time the deduction appears to be more and more an approximation of a classical way of thinking. The second Newtonian 'law', for example, is an approximation of nature from our modern way of thinking, but an approximation is vague and based on a subjective scale that one considers to be important. If rough approximation is a quality of truth, then simply by modifying the scale one can find truth in a lie. Such as: "The 19th century concept of aether is a true conception if by aether we mean that it is an approximation of the vacuum of zero point energy (ZPE)". As you can see, if we give this kind of leeway in our statements, then anything and everything is either true or false depending on how we decide to approximate the terms and concepts of our theory. That's not deduction, that's physics by interpretation.
Mathematics and logic provide us with the prime example of how grounded axioms lead to true theories. If we want the same surety in our physical theories, we need to ground our physical axioms to more than mere observation, they must be derived from absolutely true logical constructions.
I agree to a point, however I place more importance theoretical predictions and include those deductive merits of a theory as secondary. The standard model is an example of such a theory. It has over 19 or so fundamental constants that must be inputted into the equations in order for it to yield its wonderful results (not to mention it leaves gravity as a non-renormalizable theory). Not many expect the standard model to be the final word as our most fundamental particle theory.
The trick is to discover the logical imperative for the Universe to exist.
That would be quite a trick. Of course, tricks often turn out to be just tricks.