EVOrange - 11:45 am on Dec 5, 2005 (gmt 0) EVO
You just need to run tests to see which works better for you. Perhaps even, YPN will work better on some pages vs Adsense and you may end up with a mix. It's good to have a balance.
However, for my niche, YPN has not been good. I have tried it twice now and the targeting is way off resulting in dismal ctr/ecpm.