Israel Should Nuke Iran (but won't)
Iran is going to get nukes if it is not prevented. Those nukes are going to be aimed at Israel (as well as Pakistan, Eastern Europe, Iraq, Turkey...). When this happens Israel will be 10 minutes or so from destruction. To protect itself Israel is going to have to prevent Iran from gaining nukes or fall into a standoff.In a standoff the best possible outcome is one side gives up sees the error of its ways and decides to live like the other. In this particular case I think it is safe to say this will not happen.
Next best outcome is one side sneak attacks the other with sufficient tonnage to prevent any return fire. Israel has submarines and Iran has a crap navy, so Iran cannot prevent return fire. Likewise Iran has a lot of places to stick nukes (including the Gaza strip and the southern half of Lebanon). This outcome will require luck.
All other outcomes are bad. Effective annihilation of both countries or even worse a nuclear starburst where one country targets its missiles against all possible enemies.
If Israel allows Iran to gain nuclear weapons, then by definition (and discounting the impossible outcome) Israel will be committed to a course of action that will lead to the deaths of millions.
Best possible outcome requires that Israel prevents Iran from getting nukes. Israeli conventional forces are probably not capable of carrying out this task, because Iran is too far away and too well armed. However a pre-emptive nuclear strike against Iranian production facilities and research institutions will degrade Iranian nuclear potential. The research facilities will need to include universities in large cites and millions will die. However because millions are going to die anyway, and they are not Israeli, Israel is on to a winner.
Update:
On further consideration it seems unlikely that Israel will nuke Iran. To do so would risk it's friendship with America and there would be a retaliatory massed missile attack from South Lebanon. Even though these are relatively minor issues, compared to being on the recieving end of a Iranian nuclear assualt, they can be used as concrete justifications for not doing something hard right now and hoping that the future will bring a change for the good. Humanity has an innate want to be optimistic about the future, doing nothing too drastic now fufills that want.