It isnt a case of one or the other.
PPC (generally with google adwords or a MSN/yahoo adcenter account) is a method of driving traffic like CPV (PPV), Plenty of fish advertising, facebook advertising and such. These are all paid advertising.
CPA (cost per action) is the method in which you would make money. Someone fills in their details and you get paid. This is opposed to other affiliate stuff like PPS (pay per sale).
You can do both in this case:
PPC -> CPA
Any ppc company advert -> when clicked -> goes to your CPA landing page (this step can be taken out if you are direct linking to an offer) -> from your landing page to the offer.
From there, hopefully your visitor will find what they need, fill in their details and you get a lead which = money.