Interesting, sincere thank you. If my external bearings are same, that means preload is (also) loading the sides (inboard on outer race, outboard on inner race) of the bearing grooves. I need to ponder what that means in terms of spreading the bearing load better. On hub cup and cone bearings (angular contact), preload has made a huge difference to me in durability. If the external bearings are different, perhaps not. But they do come with a torque spec on the cap, and after the first retorque, no loosening for almost 2 years and counting. Whereas with internal cartridges, they just keep getting looser and looser after that starts.

EDIT: Can't yet find online, if any externals use angular contact. But did find this snippet: Internal may be stronger as bearings are fully supported by the BB shell, whereas with externals being cantilevered outside the BB shell, with the bearing carrier being aluminum and thin section thickness at the corner to the threads, taking a big huck (jump) may be more likely to fracture that carrier on externals.

EDIT: Some makers, such as Wheels Mfg, offer a choice of "standard" ABEC 3 BB bearings for BSA 24mm, or "angular contact" at higher cost.

My externals are brand-x same as my crank, so not a clue what bearing type.

Good question and comments asking about the difference on an online discussion board, but won't allow me posting the link, or even the name of the board. Discussion is titled:

Are the angular contact bearings worth the extra cost (Wheels Mfg BB)?