The larger spindle DOES make a substantial difference in stiffness, and makes installation much easier. As does the wider bearing stance. Then again I have snapped a couple cartridge BB spindles, so maybe I'm a freak. I would suspect that the larger external cup BB bearings would last longer, but haven't seen data to back that up. I will say that it's silly you can't service external BBs more easily, and that OEMs advocate that you toss them if there's a problem.