What's a PPS?
From an affiliate standpoint, I like to mix it up. Don't put all your eggs in one basket. Go for some PPS sponsors for the faster money and go with sites that are hot and you know will retain for some long revshare money. In the long run, of course, a good rev share sponsor will make you more money than a PPS.
From a program owner standpoint, I believe that strong rev share site are the way to go and offer up private PPS deals to webmasters who have proven themselves able to generate significant sign-ups.