It depends upon the niche and if it is banned niche. Anyhow, directing to landing page with presell works better. Are you new to PPC? Maybe you should use a lander to presell and collect optinn before directing to CPA offers. PPC is too expensive to just direct to advertiser. Better to create a database of opt in for remarketing later on.
Example, your CPA offer is a chane to win $100 Amazon giftcard.
In the prelander, mention get a $100 Amazon giftcard free when you opt in *T&C applies.
Below the prelander write it clearly that there must be some level of participation before a CHANCE to QUALIFY for $100 Amazon giftcard. This must be written clearly so that you play around with TOS legally putting yourself a legal protection.
When the person signup a confirmation email will be sent (assuiming you are using an autoresponder service). Once the user confirm the email, direct him to a page where it states [Want to get ANOTHER $100 Amaon giftcard? Just complete this simple survey to qualify).
See, you are basically collecting a database where you can reuse later on for remarketing. Your money spent on PPC will be better spent this way.