I think i get more CPC for text as i tried a little test and found i got more clicks with image (because it stuck out i suppose on my template, flashing away) but more $$'s for text
Well, I guess it depends on what type of site you run & where you place the ads, so there is no real best one if you are just asking generally
It depends on your site, if you have a site filled with text, it's best to blend them in with text ads. If you have sites more dominant in images, blending would be easier with an image only ad.
i prefer txt ads because image ads look like ads visitors are not coming to your site to click your adsense
hmm, I just changed my header ad back to image a few days ago, and my clicks seemed to go up. I thought image ads paid more? Can anyone verify image ads pay less?