The difference between nukes in Iran and nukes in Israel is this: Iranians are jihadists who believe in martyrdom to achieve their goals. Suicide, murder, the death even of Muslims is good as long as it furthers this agenda. To have a nuke to use is a jihadist's dream.
Nukes in Israel - are a last strike resort and deterrence. ( If they wern't, they could have used them by now . There have been instances in Jewish history where Jews have committed suicide instead of being killed or forced into conversion, but generally Jews do not believe in suicide and martyrdom.