In summary, the choice of burst type is a critical tactical decision. Air bursts are used to maximize widespread blast damage with minimal fallout. Surface bursts are used to destroy hardened targets like bunkers or missile silos, but at the cost of creating immense, dangerous fallout. High-altitude bursts are not for ground destruction but for disabling electronics via EMP, while sub-surface bursts are specialized for attacking submerged or deeply buried targets.

Source: Nuclear Weapon Bursts 1991 Navy documentary