Well, this question has been asked many times around and actually I don't think that anybody can give an answer (as simple as 'Network A') to this. The reasons are very simple:
All comes down to the traffic (source) you use. Most installers use a register key to validate if certain software is already present on the system. If your traffic already has installed lots of offers, the networks working compliant won't install anything. Clean traffic is therefore an important one. Another thing to note is that some networks optimize the offers to serve globally while others serve it based upon your traffic. This can make a huge difference in terms of conversion. Last thing to keep in mind is that the big networks mostly all have the same offers. Large public networks are difficult to control in terms of compliance for advertisers. This results in not too many advertisers interesting to go with them.
In a nutshell, there is no 'best paying network', it comes down to your traffic quality and method of monetizing. A/B testing there installers can give you a clean idea, making sure you can view statistics at any time.
