Google AdMob is the best choice in my opinion for any developer or company looking for a reliable way to monetize their app traffic and generate revenue from relevant ads displayed inside their mobile app, and it can be easily integrated into any IOS or Android App.
AdButler is suitable for any company size but I would said that it is better for small to medium-sized agencies. AdButler is highly scalable but the control panel/dashboard could be challenging to manage if you have many campaigns or many users. It's also a good alternative for ad networks, which would like to manage multiple relationships with publishers.
No special reason for choosing Google AdMob. Out point is easy to gain appropriate knowledge from youtube.com and people who work with us. We won't have another similar application so far. However, we feel it works well and makes us happy because of easy function and experience. So I recommend this if we need to apply this for our company activity.
AdButler is very convenient and very cost effective. Additionally, when you change a setup at the ad level, the server shows the change immediately; there's no delay. Ad Manager is better when you manage a significant amount of campaigns and users, but it's not that cheap in the end and you always have to wait for any change. EPOM is also a good solution, but the look and feel are old and it's complicated for some users to manage properly.
Before I got into it my other friends told me there are way better Ad providers. But being a Google fan I still signed up.
Now I remember writing to AdMob, requesting them to give me earning rates... But they never replied. So zero return on investment. They just keep you guessing.