we have shroedinger's differential equation, heisenberg's matrix mechanics, dirac's formalism, and feynman sum over histories stuff. now i may be wrong and and i really don't know anything but i think that these are all equivalent and some even the same thing. but if im going to learn QM for keeps, which is the most useful formalism? i see the point in wasting time learning one and then relearning how to do the same thing a different way. i think i might as well learn the best and just use that. any dissenting opinions on my aforementioned opinion appreciated. thx.