endgame a rough guess here and if i understand correctly, first there is no difference per say from cpc or cpm, a cpm regardless of cost will contain clicks / should do, and as such these can be calculated as a cpc costing and just about every method regardless of payment or fancy name can be put to a cpc level playing field for comparison purposes.

If you were to start with a cpm and fine tune that campaign you would have an idea about the max cpc you would want to run or vice versa a well run cpc / ctr will give you a cpm setting.

as to which one converts better the answer is none will convert better, they are the same ad and regardless of the payment banner used in the background this will have no affect on the ctr.