Which Performs Better: 336x280 or 300x250?
Google hosted a 30 minute "webinar" today, with a focus on site targeting -- creating ways for advertisers to target areas of your site to advertise on. I'll probably post about that in a few days when Google releases their summary of the webinar.
However, one interesting bit of discussion popped up in the Q&A portion of the webinar. Google advised webmasters to use the 300x250 ad unit, as that is preferred by advertisers (especially for image and video ads). However, some of the attendees said that they get a higher CTR when they use the 336x280 unit. Google agreed that it was often the case, but that you'd probably get a higher CPC if you used the smaller unit -- especially for image ads.
Another user asked if 300x250 image/video ads could show up inside of the 336x280 ad unit. Google gave a clear "no" to that. They said that advertisers can build a creative in both sizes, but image/video ads only show in the size they were created for. The text ads, of course, can float around to any of the ad units.
As a result of that, I've swapped out a few of my 336x280 units for 300x250's. I'll track the channels and see how it goes.
Any of you have previous experiences comparing these two sizes?