I was thinking CPC because only interested people will click the link as with impressions people may not even care. CPC imo would have a higher turnover for customers right?
There is a lot of things that play a serious part when it comes to creating a marketing campaign like this. Please see below.
The niche that you are targeting and the CPC.
Is the niche something that targets a wide demographic?
Is your ad copy strong enough to attract clicks?
Which would be the most cost-efficient method?
The quality of what you are advertising.
Now, I could have made a bigger list, but I would be here all night practically writing an e-book. You should really look into this a little deeper to have a full understanding as not knowing could cost you tons of money from the beginning.