It is not well known, but the Shia of southern Iraq and Iran belong to different sub-sects of the Twelver Shia sub-sect. With that in mind, from The Economist:

Top theologians, even inside Iran, prefer aloofness from worldly affairs to the late Ayatollah Khomeini's doctrine of placing worldly power in the hands of a single senior cleric. Non-Iranian Shias dream of restoring the scholarly pre-eminence of Najaf at the expense of the ayatollah's hometown, Qom. “It is in our genes as Arabs to claim rightful leadership of the faith,” says Bayan Jabur, a SCIRI official in Damascus.

When I was a child in upstate New York, the local mosque had sponsored a visit by a learned man from Yemen to give us a sermon. The mosque was 3/4 non-Arab [1]. All the non-Arabs had headphones because he was going to give the sermon in Arabic and someone would translate for us. The sheik looked a bit confused & annoyed. Before he gave the sermon, he decided to give us a long lecture (30 minutes) about how "all true Muslims know Arabic. It is the tongue of the prophet, the language of God." He was positively distraught and seemed like he was going to shed tears as to the blasphemy of it all (in hindsight, how learned could this guy be to be shocked that non-Arab Muslims didn't know Arabic fluently???). I was 9 or so, and rather confused. My father and all the other non-Arabs were stoic about it. After he was done bitching us out he gave us his sermon, though grudgingly. He talked about how Muslims would go paradise would conquer all before them at some point-standard fare-nothing our imam, who was a nice guy, didn't tell us every week (OK, my family generally went on the holidays, though my dad showed up now and then). No one complained about the outburst except for the big black burly guy who drove the bus for the "Sunday School"-I could hear him bitching out our iman about why we spent money on this guy when he totally disrespected us. In Mauratania & Sudan, states with large non-Arab indigenous populations, the Arabs enslave those not genetically destined to rule (the Berbers of Morocco and Algeria aren't quit treated the same, though there must be a reason that they tend to oppose Islamists). In the Gulf Arabs treat the Indians, Filipinos & other non-Arabs (and Arabs from non-oil countries to be fair) like indentured servants. The Filipinos, as dirty non-Muslims, have the privilege of being beaten and raped now & then (non-Muslims are screwed in their legal systems often). How do I know this? Not just reading about in the papers, a Saudi student came up to me in college and explained to me how he liked Bangladeshis since we cleaned ourselves, and weren't dirty & lazy like the Filipinos who needed to be beaten to get work out of them. I think we can understand why the Kurds are one of the few philo-Semitic Muslim groups-they have lived under Arab domination [2].

Muslims in South Asia are correct to criticize Hindus for their revolting pre-modern caste system. On the other hand, they must admit that a tacit caste system exists amongst Muslims. Sayyids, descendents of the prophet, have cachet. Arabs are respected as teachers, and their version of Islam, generally pushed by the Gulf Arabs with their Wahabbism, is given precedence over the interpretations of non-Arabs (Turkish Sufism for instance). Southeast Asians like Mahathir Mohammed might talk about taking leadership of the faith, but I've heard Malays talk about how their Islam is better than that practiced by their Indian brothers because they received it directly from the Arabs [3]. I've talked to idiot Bangladeshis who take pride in their Arab ancestors, real or made up (our non-Indian ancestors are far more likely to have been Persian, Afghan or Turkish-and most Muslim Bangladeshis are no different than Hindu Bengalis in India). My father, a moderate on religious questions, admits that Arabic is the "most beautiful language in the world," but he goes on to declare that "its grammatical structure is perfect and pure." He did speak Arabic fluently as a child, so I don't know whether to believe him or not. Islam is the brotherhood of believers, and it practices that quite a bit. Nonetheless, I feel that Muslims, especially the malwali people (the converted people-of course, Arabs had to convert at some point too!) , tend to downplay that there is a stratification and perception of spiritual purity.

[1] The division of labor at the mosque: the Arabs were Sunday School teachers and and religious functionaries, the blacks drove the buses and did all the low level work necessary to keep things going and the South Asians provided the financing. This was in the mid-1980s when the South Asian community had a higher portion of college and post-grad educated types, not many cab drivers and what not at the mosque.

[2] Saddam in his speech last night talked about the attack on the "Arab nation." Iraq is a member of the Arab League. This neglects the fact that the Kurds are 25% of the population and speak an Indo-European language. The Baath Arab nationalist ideology by definition excludes these native Iraqis but reaches out to Arabs in other nations.

[3] North Indian Muslims did get their Islam from the Turks and Persians. Turkic and South Asian Sunnis share the liberal Hanafi legal tradition. They dealt with non-Muslims, so the stricter types would tend to be more difficult to jive with dhimmi and often pagan peoples that these rulers dominated. Some South Indian Muslims though probably get their Islam from Arab traders, for instance, the Mopillas of Kerala, that form about 20% of that state's population. Additionally, the Malays got their Islam from a host of sources, including, Indian, often Gujarati, merchants-in addition to the Persian and Arab influences. Mahathir Mohammed's father was an Indian Muslim, so he is probably aware of this.