In my opinion, it depends on the market you are targeting.
In some markets you won’t see many players spending top dollar on casinos and poker. In those cases, CPA could be better for you.
But if the idea is building long term relations with the casino and poker rooms, nothing beats Revenue Share. In the long term, you could be able to offer better promotions and negotiate terms with AMs.
One good idea would be using split trackers and testing the waters.