I've tried 3 of them, and I can recommend 2 of them. I do make more money with join4free because of the remote signup boxes.
Freeezinebucks doesn't allow remote signup boxes, but they have so many different niches that you can target them better anyway if you have the proper traffic.
Both have exit consoles. Join4free tamed them down so they are comparable to the others now. They used to be pretty bad for exits.
FEB pays $1 per email with no deductions. Join4free pays $1.15 per email or I think $.85 if you use the remote signup boxes. (Up to $1.30 if you can send more than 100 signups a day.) You get deductions with join4free. Average is 20% but mine are much less than that.
Like I said, I make more off of join4free with my traffic, but if you have better targeted stuff use FEB.
Try 'em out for yourself:
http://www.freeezinebucks.com/ps.php?s=feb&u=evildick
http://www.wegcash.com/?wm=evildick