You have different titles and buildings (with more or less the same behaviour and game mechanics), you have completely different events which give the flavour of playing muslim (going to mecca and all) and you have specifics that improve the experience (up to 4 wives, decadence mechanics, different religious CB, easy to wage war against people of different faiths and regency even if adult when you are on holy trips to mecca). The difference from playing catholics is bigger than playing orthodox after LoR.
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I've started in 1170, or 1171, when Saladin (Ayyubid) gains the sultanate of Egypt. I think you can start earlier with him, but didn't wanted that. I'm exploring different scenarios from a few save points that are good turning points.
The main purpose is to play fair (the legacy of Saladin) and restore an arabian empire, the total islam/arab state controlling most of the territories the ottomans or the caliphs had at their height of their expansion.
Now, I'm exploring a different version, where Saladin married the daughter of the BE's (ERE) basilios (had to cheat that one because of the infidel penalty, but I have a very good diplomat as grand vizier, so given time that might be achievable anyway, unless she would have been wedded to someone else in the mean time). She's born in pink and already gave me a son. I just want to see if possible to gain christian land like this, then I'm returning to the thread where I don't do this

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Challenge you want?
Play as something less than emire. Try a sheikh in a difficult position. Emirs and definitily sultans are too authocractic, have to many easy mechanics to subvert turbulent vassals (I've taken away the title of emir as Saladin the sultan to someone who willingly accepted to be my vassal; I did that because he declared war on the caliph of the sunnies - which btw gave that lowly emir no penalty - oh the decadence).