So I can conclude from this thread discussion that Ad unit and Link unit both are effective depending on ad placement and website Layout. Ad Units performs better in post, work better just above article content, and at the end of the article. Link Units performs well below header and in navigation area and on the sidebar.
both ads are similar in results. but the placement varies that is ad unit is situated best in top of the page/post. where as link unit is good at below the image of the post
I prefer ads units. With links units I don't like that visitors have to click two seperate times before the site owner gets paid. Just my 2 cents.....
I use both on my pages. But Iput the link units in my menu area so my pages don't look overloaded with google ads. To tell which are getting more clicks and making more, just add a channel name when you are creating these at google. That way you can tell how each type is doing under the top channels menu. I find my link units, the simple text get more clicks but pays less. And the text Ad units get clicked less but pay more. Each have their advantages. I stick with Ad units in my content. And Link units in my menus. Both seem to work great.