Provide a detailed theoretical breakdown of the Many-Worlds Interpretation (MWI) of quantum mechanics. Contrast it specifically with the Copenhagen interpretation regarding the collapse of the wavefunction. Address the problem of basis ambiguity (preferred basis problem) and discuss how decoherence theory attempts to solve the issue of why we perceive a definite classical reality emerging from a universal wavefunction. Discuss the theoretical implications of 'branching' universes on the conservation of energy and information.