According to a recent study, a nuclear exchange with Israel would be vastly disproportionately damaging to Iran.

Jerusalem Post:

If a nuclear war between Israel and Iran were to break out 16-20 million Iranians would lose their lives – as opposed to 200,000-800,000 Israelis, according to a report recently published by the Washington-based Center for Strategic and International Studies (CSIS), which is headed by Anthony H. Cordesman, formerly an analyst for the US Department of Defense. The document, which is largely theoretical due to the lack of verified knowledge in some areas – specifically in terms of Israel’s nuclear capability – paints various scenarios and attempts to predict the strategies of regional powers, as well as the US.

The report assesses that a nuclear war would last approximately three weeks and ultimately end with the annihilation of Iran, due to Israel’s alleged possession of weapons with a far larger yield. Israel, according to the assessment, would have a larger chance of survival. The report does not attempt to predict how many deaths would eventually be caused by possible nuclear fallout.

Even if Iran gained the means and knowledge to create nuclear weapons, according to the report it would still be limited to 100 kiloton weapons, which can cause a far smaller radius of destruction than the 1 megaton bombs Israel allegedly possesses.

Possible targets for an Iranian strike are the Tel Aviv metropolitan area and Haifa bay, while the list of possible targets in Iran includes the cities Teheran, Tabriz, Qazvin, Esfahan, Shiraz, Yazd, Kerman, Qom, Ahwaz and Kermanshah.

Conventional wars between Israel and Islamic adversaries have produced similarly one-sided results, so it might be unwise for Iran to dismiss these particular conclusions.