Solo ads...affiliate swipe file versus allowing the solo ad provider to create an email

Hi there,
I’m curious, has anyone here tested the difference between letting the solo ad provider write the email or use the affiliates swipe file? In the training videos, that I’ve seen so far, we are shown how to send the swipe file to the solo ad people.
You would think that the solo ad’s guy would know HIS EMAIL audience and know what to ask of his subscribers. Just a thought, any ideas on that?