In reducing the number of warheads, down to one per missile in some cases, the weapon is lighter and has a longer range. It can also be targeted more accurately.By reducing a missile's payload to just one warhead, the possibility of actually being able to use a nuclear weapon is also increased. You don't have to let fly three or more when you only need one. This adds to the difficulty of an enemy's calculus.
What is not mentioned is deployment of cluster neutron warheads.
Modern neutron weapons produce almost no explosive yield from fission, the fusion release having been greatly increased with respect to the fission trigger. This virtually eliminates fallout by virtue of both the greatly reduced fission component of the release and the minimal explosive effect. In the most modern systems the fission trigger is replaced with special irradiated metallic fulminants (and lately by electronically pulsed proton spallation), reducing explosive yields to those of a hand grenade and less.
Unfortunately, neutron flux is radically attenuated by the atmosphere in comparison with heat and other radiative effects characteristic of explosive nuclear weapons. To achieve a wider-area effect, you have to spread the neutron sources, thus the clustered release of independent bomblets according to target characteristics.
I have always felt it quite likely that I would live to see the use of nuclear weaponry in war. As time goes by I only see those odds increasing. This is partly a function of the increasing irrelevance of TNT tonnage equivalent measures traditionally used to class nuclear weapons.
The larger cause of these rising odds is the exponentially increasing density of technologically advancing human populations frequently characterized by irreconcilable worldviews.
The good news is that I made some of this up. The bad news is that I didn't make it all up. Nobody knows what the future holds, but it's pretty scary from my point of view.