Text Ads or Image Ads? Which are better?

There are two types of Ads: Text Ads and Image Ads.
It is very important to know which type of Ads should be placed where and what size should be used.
Text Ads:These Ads are relevant to subject of your blog.If you have published text Ads, the visitor gets more choice to choose the Ads.It is therefore the best Ad type.It has been found that most of the webmasters earn the most from text Ads.
These Ads should be placed very near to the content of blog.Placing above and besides the post(content) works really good.Use of large rectangles, small banners look better in point of view of the visitor.

Image Ads:These Ads do not offer much choice for your visitor to choose the Ad from.The image Ad generally consists of a single Ad.
These Ads may be placed as a sidebar or top banner.Because the visitor gets attracted towards it quickly, placement should be done in the sidebar.