A smaller number of nukes might increase the likelihood of them being used, if their use wouldn’t guarantee total annihilation of either side. They might become a tactical option, because even if you get nuked back, you might still live to fight on.
Ideally we find the number that still effectively guarantees MAD but is currently smaller than what we have now, so at least it won't cause extinction but will have the same deterrence capability. Do we really need 1500 nukes on either side for full deterrence? Wouldn't 500 do the job?
Still safer for the world in general though.