It depends on which geo you want to run as all networks have their strength and weakness. It will also depends which deal you can negociate as it will greatly impact how best a network can be as in best we usually mean the one with whom we can earn the most. For example in NL Campeon are really good, very honest, great network with great people, revenuelab are also quite good on some geod (they help you negociate the deals with the brands)...
If you need more info don't hesitate to PM me I have been into gambling using seo for sometime.
Cheers