The main reason for thinking that nuclear war would be worse than Soviet domination where future generations are concerned is that nuclear war could lead to the extinction of the human race, and it is considerably more important to ensure that future generations will exist than to ensure that, if they exist, they will not exist under Soviet domination.
Jeff McMahan, Nuclear deterrence and future generations, in Avner Cohen & Steven Lee (eds.) Nuclear Weapons and the Future of Humanity: The Fundamental Questions, Totowa, New Jersey, 1986, p. 331