One thing that Hambini says is that most friction from sealed bearings is from the seals. In my experience, comparing the rolling resistance of old Campy Nuovo Record-hubbed wheels (angular contact, no contacting seals) I think that's right. I agree with the Enduro guy that AC bearings are going to last longer than deep-groove ball bearings. Because there is axial force in riding and in preload on bike bearings, and preload on deep-groove ball bearings puts higher stress on bearing races. Deep-groove radial bearings are great for .... radial forces (duh!). AC gives you some support in the axial direction. It is interesting to note that Enduro's warranty claims dropped substantially after moving to AC.
I have a pair of Campy nuovo record wheels (AC, that is, cup and cone) that have lasted 30 years. Anyone get 30 years out of their DGR cartridges?
I'm kind of surprised that AC cartridge bearings haven't taken over more completely. Clearly the asymmetric forces in graunching the crank induces side force, so its easy to see why AC last longer in BBs. But what about wheels?.
Frankly, I think that the wheel and bike mfrs took to cartridge DGRs almost entirely to create a new revenue stream for them and their dealers.