one off is a good option if you have exact idea of the sites on which you want to advertise as an advertiser but as a publisher you need to analise your traffic first to pick out of these two.
Payperclick is attractive. But I prefer cash for my clicks and I am not interested in doing it for points. Payperclick ads are encouraging. GOODSAMARITAN
I prefer one-off. Paying $100/mo for a banner on a very similar site can do wonders & bring in a lot of targetted traffic & will spread the word about the site which is being advertised.