I'm not sure if there is a definite answer to this question. I have used both Overture and Adwords in the past. I've seen them both generate conversion well. But is there a better program between the two for business to consumer?
I personally can't say definitively in generalizations like which is better for b2b or b2c. However, there are definitely differences. And content networks also make a big difference. It seems each campaign we do swings one way or another. Your best bet is to test test test. Track your conversions by engine, and by content network. Your personal findings will give you your answer.