I think it’s a very good idea to have some revenue share and some CPA. You’ll have to look at all the affiliate programs you have and choose which fits on either side.
Some people here says that microgaming has the better player retention and others say that playtech is the better. It depens on the traffic you have and the exposure you have for each casino. It’s impossible to say anything about any program without having a look at the site and exposure of casinos.
The only thing I know is that it’s a good idea to try both CPA and revenue share, see how it goes, and then modify as needed.