It must be considered, in case a war is being planned, that Iran has a population of 80 million that are proud of their Nation, its history, culture, and civilization and would in case of any external threat flock whole heartedly to protect their homeland regardless if they like or dislike the current regime. While on the other hand out of the 30 million people that live in Saudi, 10 million are foreigners that have no particular allegiances.
Militarily the Saudis may have aerial superiority but Iran has already acquired the S-300 and developed its own Sayyad defensive ballistic missiles and so any aerial superiority is only nominal.
An important factor that needs to be considered by the Saudis is can they rely on the loyalty of their Shi’a subjects in Qateef whose areas are unsettled as I write this very moment. Be sure that they will cause a lot of problems for the Saudi State, and they constitute about 15% of the population. What will cause great harm to the Saudis is the Wahhabi stance towards the Shi’a, whereas in Iran the Shi’a clergy are much more tolerant of their Sunni counterparts, whether they be Kurdish, Turks, or Baluchis.
The chances of a full blown war between both sides are next to none, if any confrontation does occur it will probably be limited to exchanging ballistic missile strikes in which case the Saudi stamina is far weaker and smaller than that of the Iranians. As there are only so many petrol refineries and water desalination units in the country coupled with the fact that Iran has the second largest stockpile of ballistic missiles in the Middle East after Israel, and so Iran’s chances of success are greater in wining and standing its ground during the war.
The Saudis are relaying on the Americans to help them, even to do some of the fighting, while US geopolitical interests does not align with such fanciful dreams as they have Naval bases in the Persian gulf that they would like to maintain. There are 11,000 US soldiers in the Gulf these Marines are in danger the moment the US gets involved in a conflict with Tehran.
The US may have in days past protected the Kingdom in order to secure the oil resources, but with the advent of shale oil it may not be worth the risk for the US to get involved in an armed conflict. The very nature of long range ballistic missile wars would restrict the options for any potential Saudi ally to intervene as the outcome of such a war would be strategic and economic bleeding of any country willing to participate. It is important to note that Saudi Arabia’s only ally is Bahrain, the rest are there for the show and some are even digging a hole under the Sauds, a good example is Qatar. It is highly unlikely that any country would attack the other; instead they will revert to their favorite hobby, proxy wars.
Iran’s strategic depth is far greater than that of Saudi, meaning, Iran has many vital organs of the State that are scattered across the country. While Saudi Arabia could be crippled by targeting a handful of geographic positions, by destroying Jeddah and Riyadh, Saudi Arabia would cease to exist while in Iran there are many such seats of power. Iran’s borders are safe with the exception of Baluchistan, while Saudi faces dangers from the South in Yemen, the North with Iraq and in the East due to the large concentration of the Shi’a population in the oil rich province of Qateef, and let’s not forget Qatar.
The future of Iraq, Syria, Lebanon, and quite possibly Oman is directly tied with the fate of Iran and in case of war they would come to Iran’s aid financially, logistically and politically. Iran may also draw support from central Asia i.e Armenia and Afghanistan and also from Pakistan as there are many who sympathize with the Iranians.