None of them. Stick with in-content text links and maybe image links. I do very well with Amazon so I know this from experience.
Yeah the Amazon widgets don't do so well; however, if you are building sites on Wordpress you can get a plugin from Code Canyon called Amazon Hotlists and put that widget into your sidebar (it converts). It pulls products from various lists that Amazon produces by browse node so you can for instance get the top ten bestsellers in the off-road motorcycle tire browse node.