You can choose any of them
I personally worked with PropellerAds Media. They are good CPM rate for interstitial ads. If you are getting traffic from USA, Canada and Europe, you can make good money with them.
I’m currently using Heyzap with Chartboost/Admob, they say the find automatically the best network to serve the ad based on some intelligent system, but in my opinion all what they do is to serve their own ads, i’m getting less than 1000 impression on chartboost, even if I belive chartboost’s ecpm is better than heyzap’s one, they prefer to serve their own ads.
so basically, I just changed ecpms manually today to smth like this admob>chartboost>heyzap and i hope to see good results tomorrow, otherwise i will forget about the mediation and work on making my own code to mediate chartboost+admob ( the best 2 networks out there )
Have your considered including AdBuddiz on your list? We are specialised in high-paying premium full-screen interstitials. You can use our solution in parallel with other ad networks, to test how it works. Since we are reluctant to display ads when the payouts from advertisers are too low, my suggestion would be for you to display our ads first, and fall back on other solutions afterwards. This way you’ll maximise earnings per install & fill rate. By the way, some of our campaigns also pay per impression
We have over 15 000 publishers in our network and are 100% Google compliant. The integration of our SDK is really easy; only 2 lines of code to paste. We also provide support 6 days a week