ha! which is better of the two? that's a debate right there. in my opinion, MOS is better. even aside from the fact that BR was never intended to be an origin for continuity, and was almost immediately ignored by canon from the beginning, MOS was just a better story. but even as of late, MOS has become increasingly obsolete, for better or worse. currently, Geoff Johns and Gary Frank have been producing a title called "SUPERMAN: SECRET ORIGINS". for the immediate future, it will likely be the most referenced as canon. some people take issue with it's references to the donner films, but over all its been quit a solid read so far. i believe 3 of 6 issues have been published and shouldnt be hard for you to pick up. after that, there are lots of worthwhile trade paper backs you can go and read. i'd recommend anything by greg rucka or geoff johns.