Doesn't it boil down to, how much you trust the HD ?
Doing a full format instead of a clone or a quick format will check/use 100% of the space.
This makes the HD work harder, and usually, will find more issues (bad blocks) than just a clone or a quick format would.
Yeah, it takes forever as the sizes keep going up, but there is no way around it.
Some people even do HD 'tourture tests', on the theory that if the HD was to fail, it will do so in the first X days of being tortured, and that most failures happen on a bell curve.