Ceramic balls are used in bearings to allow better acceleration. If the bearing is accelerated quickly, heavier steel balls may not keep up, and will skid on the races causing wear and heat build-up. However, we use them for other reasons, because we don't have that problem, especially in diffs.
Ceramic balls are harder, and therefore not as easily damaged by dirt and dust that can cause steel balls to get indented, or develop small flats if they skid (because of the dirt and dust).
In diffs, use the hard (dark) ceramic balls, not the white or grey ones. Corally make the best I've ever used. Nonetheless, even the Corally balls can crack in TC diffs because they run under higher pressures than 12th or 10th Pan Car diffs. Partly because the pan-car diffs are larger diameter, partly because they use larger, or more balls, and partly because pan cars are much lighter, ceramic balls might not be the best ones for TC and Off-Road applications. We have a couple of drivers using steel again to avoid the cracking problems.
In bearings, the ceramic ball is helpful as it wears better, but it still uses the same steel race to run in. In that respect, the bearing may not last any longer than a steel one, because instead of damaging the ball in a crash, or when dust and dirt gets in, it will damage the race.
My choice, after wearing loads of them out in 12th, is ceramic diff balls and thrust race balls, and steel everything else - cheapest option and best wear rates. HTH