bearings are for rotating [spinning in a 360 degree circle] parts, bushings are more suited for parts that go in a "back and forth" motion.
my reasoning is that the bearings will wear evenly, as they will spin their complete diameter over their lifetime, therefore lasting longer than if they just went "back and forth", wearing on only part of their diameter. [and retaining race or part] think about a u-joint that has no grease, and the brinnilining that takes place on the cross, which is those little "lumps" or lines that are formed by the needles not rotating their complete diameter on the joint cross.
just my opinion. your mileage will vary.