Asking which of these programs is the best is like asking whether a per sign up, or partnership, or per click, or per active program is the best.
The answer is it depends on your traffic.
CE and WEG have higher payouts per email, plus they pay $15 per upsell and have nice little bonus features.
BUT
They also take deductions if your subscriber "opts out" within a certain number of days.
FEB pays out a lower per email amount, but they don't take any deductions.
Plus, you also need to read the fine print in all of their TOS's. Do they credit you for signups from free email accounts like yahoo, hotmail etc?
Do they allow signups from your foreign traffic or do they just redirect your foreign clicks to a dialer that you don't get paid for?
Its just like picking any other type of sponsor, send traffic to a bunch of them, and then stick with the one that nets you the highest check at the end of the month
