I know there have been hundreds of threads about which CSAs are the best, but I have yet to find one that talks about which are best for OCC. I have not played much OCC, but here are my thoughts:
1. Militaristic
I normally dislike this advantage, but in OCC the lack of more than a few cities makes it very costly to spend 50 turns in a city building a wonder. THis makes GLs much more important because they save this time; without one wonder-building would be practically impossible. I consider the extra 2 or 3 GLs from being militaristic invaluable.
2. Industrious
The worker advantage is huge, because being able to build roads out to colonies is essential. This is normally a very good trait, but OCC makes it even better.
3. Scientific
I haven't played that much OCC, but science must get very difficult especially later in the game. Quicker libraries and universities would help a ton.
4. Expansionist
THis one is unpredictable. If it ends up giving you nearly 10 or even more techs, it might be the best of them all. WHen it doest give more than 1 or 2, it's the worst or second worst. The few techs it always gives can be useful, but not as useful as the scientific advnatage which lasts the whole game.
5. Religious
Yes, believe it or not, religious is 5th! As mentioned before, wonder building is quite difficult and a cultural victory will be tougher than it might seem. The gov't switching is useful, but I usually use culture to gain territory through flips or expansion, both impossible in OCC, so this advantage (which I would prabably put in 2nd normally) is way back here.
6. Commercial
The entire advantage except the very small and insignificant city square bonus disappears. There is documented evidence that this advantage ONLY helps city quantity corruption. SInce there will never be more than a few cities, this CSA is pretty much useless.
This means that the best 3 civs are:
1. Chinese (mil and ind)
2. Germans (mil and sci)
3. Persians (ind and sci)
Now everyone come and explain how my order is completely wrong