From my experience, 2 ads may be better with more earnings but 1 ad is better in user experience so that you site doesn't appear made for adsense.
I would give a vote for 2 ads as well. However, there are factors involved, including your own audience type and overall theme layout. Some theme might works well with 1 ads over 2 ads anyway.
Difficult but i think i will vote for 2 ads. Sometimes your lucky and sometimes your not, there is no reason why it really should be better.
Just 1 ad above article, because 2 ads wrapping around text are just too much... ruins the user experience