How can I know which one will perform better? if I am using a 336*280 box for my website and the content has got most part text and 2-3 images on the whole page... any ideas?
One way to find out is to setup a text only ad unit and image only ad unit and place alternately (one each week/month) at same location on the same page. That way, you can find out which one performs better in term of cpc
will analytics help with that if it is provided to us easily telling an image ad is shown and now a text ad is shown!