What types of ad is better ?

I can say that it depends on the position. I use text-ads just after the content, and sometimes in between content. Image ads for the header position and right/left navigation. This is what works for my, and it's not a general case. I suggest to test for a while and see how your CTR is performing.

 

Actually, you could check your adsense report and find the most earning type. Actually, the most like of my blog is contextual ads. However, I continue use the both type because I think that may better for me.

 

large rectangle and medium rectangle add work best for me.

 

Image ads are preferred by me the most as they give better clicks.

 

Some times ad placing is also important. Also may try the recommended text and image add

 

You can use both ads on your websites or blogs. I think Text ads good for better earnings. Keep in mind that Google recommended to use both Ads.

 

Use Both TEXT/IMAGE

 

Use Both Text and Image ads as it is recommended by Google also

 

Again, the key to success is Testing. Test different types, positions on different pages. Sometimes even the smallest change can make a difference.