The same question has been asked million times before and the simple answer is; the choice is upto you!
Pay per sale may work well for me but it won't for you, depends on the content you upload, where do you spread your links...etc
To make it easier: use each plan for an entire week then you will be able to decide which one gets you more earnings. :P
If you have a good site use pps and get sales
If you post for public forums use ppd for downoads