Airbursts are generally used to maximise the area damaged at the cost of peak damage - so for soft targets like cities. Ground bursts would be used for hard targets (deep bunkers, missile silos) that are relatively small but hard to kill. I suspect in wartime fall-out wouldn't be a major factor in planning all out attacks whereas it was a big factor in atmospheric testing.
I also wonder how dangerous fallout was considered to be, in the long run. I have the impression that up into the late 60s fallout was considered dangerous in the short term but not after say a year.
