Scott's got the right idea -- without going too technically (sorry my degree is in Mechanical not Electrical Engineering) - the BEC circuit is being processed differently - what you see as that processing difference is external caps instead of internal.
Its really amazing the amount of energy these little motors pull. Really low turn modified motors (4.5 in mod touring), 550 motors on 4wd SC, 4-pole motors on 4wd SC - that is where the difference are made.