The main contention between the supporters and those against the Iran deal centers on whether the agreement has enough safeguards to prevent the building of a nuclear bomb. I would question if Iran really wants to have a bomb.
Iran has signed the Nuclear Non Proliferation Treaty, which Israel has not. The activities detailed in the November 2011 International Atomic Energy Agency report which some have characterized as proof that Iran was seeking to develop a nuclear bomb was not directed at any specific nuclear weaponization.
The supreme leader of Iran, Ayatollah Khamenei, issued a fatwa against the use of nuclear weapons and other types of weapons of mass destruction. All Muslim Shia grand ayatollahs have issued the same fatwa. It is difficult to imagine any Iranian leadership defying the wishes of their Supreme Leader.
Even if the religious leadership was trying to pull the wool over the eyes of the world and the Iranian military was able to deceive UN inspectors and various international intelligence organizations including the CIA and Mossad and secretly developed a bomb, what would they do with it? Iranians may be ruthless but they are not stupid.
The Iranian military knows that if they attacked Israel the retaliation by Israel and the United States would obliterate them from the face of the earth. In the end many more Arabs would be killed then Israelis.
For Iran becoming a nuclear state would cause isolation and reinstating devastating sanctions from which their economy would never recover.