Ottomans change religion

[PotatoPope]

As the ottomans, is it worth changing your religion

[Dorch]

not really, sunni is very powerful mechanically speaking, plus most conquerable land is also sunni

[PotatoPope]

Thanks, wanted to see what someone else thought

[Arcium XIII]

It can be worth changing for a few reasons. Foremost among these is the fact that the Ottomans can quite realistically become Emperor of the HRE if they flip to Catholic, or Coptic/Orthodox in the case of the Peast of Westphalia firing. In a world conquest game, this gives you the option of "conquering" the HRE through Imperial Reforms, rather than through outright conquest. Another religion very worthwhile to flip to is Coptic, given that the bonuses from Coptic Blessings stack very well with what the Ottomans want to do.

If you do flip religion, you're probably going to have to take Religious Ideas (though they're hardly bad, especially since flipping Coptic means Deus Vult is going to give you a CB on everyone outside of the Ethiopian region) to convert the Sunni provinces; the number of bonus missionaries you get from the various holy sites you'll acquire mean that you'll be better off converting land before coring it in many cases.

Sunni's mechanical bonuses are solid, although they're probably not that much better than Catholic (free stability from Papal Influence is huge, if nothing else) and they're definitely not better than Coptic Blessings, given that Ottomans start in the position to easily acquire the sites held by QQ and the Mamluks in wars they were probably going to fight anyway.

Aggressive expansion is a bit of a neutral point in this argument; flipping to Christian makes expanding into Europe easier, and means that you can actually conquer into the HRE without automatically triggering coalitions, while staying Sunni makes expanding into Asia and Africa less taxing on the AE. Given that the European nations are the bigger threats most of the time, I'd actually consider being Christian superior for managing AE, but there are pros and cons to both.

The single biggest reason to stay Sunni isn't to do with Sunni itself, nor the land you're going to conquer, however; you stay Sunni to keep the unique Ottoman government type that allows you to maintain consistently above average rulers. While it can be worth giving this government type up, given the aforementioned bonuses (especially if becoming HRE emperor is plausible), and there are other ways of obtaining excellent rulers (one of these days I'm going to play a Hindu Ottomans game for those beautiful unique Hindu ruler stat events), it's the single biggest cost involved in flipping the Ottomans to a different religion. Because of this, unless you're implementing a strategy that very explicitly needs to be a different religion, the default should be staying Sunni to keep your government type. If, however, you want to do a specific thing involving another religion, the gap isn't so collossal that you can't justify changing, since it can be worth it for certain strategies.

[Quicksilver]

Being Christian also gives you access to personal unions + succession wars which can be powerful.

[zethomas2]

Being one of the Christian religions will also allow you gain the Dues Vult CB (best cb until imperialism) on most countries in the game. Also Coptic might be marginally stronger than sunni

[mischa.zehnbauer]

Tsaeb's summary is very good. I'd like to add that it also depends on your DLCs. Coptic realy shines with Rights of Men DLC, Hindu and Protestant need Wealth of Nations/Common Sense and without Cossacks changing your religion is a lot more difficult.
On the other hand, Ottomans special government is also a feature of Rights of Men DLC.

In the end it depends on your goals for the campaign. A casual, succesfull game can be done with any religion. Sunni is straight forward and you don't have to worry about heirs and religious unrest. Christian faiths have more potential, which is especially important if you want to go for World Crusade, but you have to invest a bit more thought into the game.

[Illyrien]

Coptic also have access to one more missionary. So its pretty easy to get 6 missionaries and decent missionary strength, without taking religious ideas. (Start + 4 sites + defender).

[Fellini_Fiend]

Copt-tomans is a very OP way to play with the most OP nation in the game. It's ridiculous really.