I posted something the other day referring to this, but I probaly should of been more clear. I hear fastclick pays the most? I mean what services pay the best?
I think it's not that easy. It all depends on your site, the subject of your site, the countries of your visitors, etc... Some PPC companies are good on certain niches/countries and some on other niches. You should try a few of them, and make sure their payment methods is what you need.
I agree you should look for payment method, at the end clicksor, exoclick, bidvertiser all pay nothing, choose the one that pays faster and less, you should stick to the big guys for high paying keywords