Coming back to the Arabs-Persians-questions. I guess the major advantage for the Persians is their gaining stability with every city conquered. Playing as Persia, stability concerns dont matter ever.
But playing Arabia, even conquering Egypt, Greece, Persia, Carthage, my Empire soon crumbles.
By the way: It's very nice to have the the Spirale minarette and the University of Sankore as Arabs ... its the easiest way to money and research besides Shrines... ;-)