Radial and angular contact bearings look identical on the outside but differ internally. Angular contact bearings have angled inner and outer races that apply pressure (preload) to the ball bearings in the middle. Radial bearings have grooves on the inner and outer edges in which the ball bearings ride in, making them less affected by differences in alignment and preload as angular contact bearings. Angular contact bearings are thought to be longer lasting than radial bearings, but only if the bearings are preloaded properly and evenly. A small misalignment in a frame, or too much or too little preload force applied to the bearings will result in much faster wear than radial bearings.
Radial bearings are more forgiving, this is because the non angled surface helps reduce stress on the bearing cartridge caused by the weight of the load (you and your bike). Hellbender 70 bottom bracket bearings are radial. All of that being said, the real killer of radial or angular contact bearings, is corrosion.