I suspect that, all else being equal (quality of material, internal finish & fit), the sealed bearing will last longer 'cause the seals (sides) of the cartridge bearing force the grease back into the spaces between the balls (rollers, etc.) as the bearing is turning. In a cup & cone bearing, the first rotation forces much of the grease sideways, out of the spaces between the balls, where there is nothing to push it back (hence the need to repack occasionally even if the bearing isn't contaminated w/dirt, etc). That's probably also one reason for the slightly increased rolling resistance of the cartridge bearing ('tho the Phils & old SunTour 9000 are awfully smoooooth!)... the balls are constantly rolling through the grease. The cup & cone bearing always rolls easier after the first revolution pushes out most of the grease.