I think that all depends on what you are looking for. Networks like CPA Empire, Azoogle and Hydra are for people who are looking to make money in the short term. These ad networks change their offers on a daily basis and are looking for a quicker turnaround themselves, they are also (in my opinion) harder to gauge as far as trends go. Yes there are seasonal trends but they dont necessarily match up with trends you would find on other networks like Cj and Linkshare.

CJ and Linkshare are about building relationships, it is more flexible with the merchant meaning there is room to try new things. Also these 2 networks have merchants that are in it for the longhaul, meaning you have a chance to build a relationship with them, which in the long term can be more beneficial.

i think each have there own pros and cons, but if you want to learn affiliate marketing i would go with CJ, Linkshare, Performics first, simple because of the amount of programs there are. You can really learn by trial and error whats works and when you take this knowledge to networks like CPA empire, etc… you already have an upper hand.