I'm not sure which would give you a higher CTR, you would need to test for yourself. However according to Google if you select to display both you will increase your earning per click as they only display the highest competing ads.
Both work well but it depends on the site layout. Try placing both of them on your site, and just test to see which works the best.
But IMO text ads have higher CPC...... than banner ads... You should try each of them and see what works well on your own blog
It purely depends on the niche of a website. It is a nice idea to place one text and one banner link in a webpage as maximum three ad units are allowed by google
I think trial and error is the best way to find out the best option. One technique never work perfect for all. Which technique is magical for one, that may not work well for you. Better, find out the best option for you by yourself.