I always found myself asking the same question. I think it all depends on traffic quality and the content on the site you are promoting. With targeted traffic I tend to do revshare as the rebills are generally good. With traffic that isn't so targeted I will do PPS. Also, if the sponsor doesn't update the site very often, you can assume retention won't be that great so it might be a good idea to do PPS. This of course differs from sponsor to sponsor.
Sometimes it might be good to start with revenue share, see how member retention is, and base your decision off of that. But if you are getting like $30 CPA, you could make $30 off of that person if they rebill only once ($15 avg/month depending on rev percentage and monthly fee), then have the opportunity to earn additional money on them if they continue their membership. I've heard some webmasters say they got out of Adult years ago but still get checks from rebilling customers.

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