Ok, well since I am yet to try YPN out, I cannot make valid comparisons. I've not experienced being a publisher for Yahoo as of yet, so everything I know about them I only know - not from experience - but simply from hearsay.
Yet, I'd like to leave my opinion.
First of all, the fact that Google Adsense is open to publishers all around the world already makes them way much better than YPN - stated very frankly from a publisher's point of view, of course.
Now, next point is - earnings. Since I've only ever tried adsense, I can only speak for its behalf. Earnings used to be good, but if your niche is overly saturated, it could be very challenging indeed to raise your site's CTR, as well as traffic. If you don't have enough traffic, and clicks are limited, you could really earn very poorly with Google adsense.
But from what I've heard with Yahoo, they pay publishers pretty high. Still, only hearsay.
I honestly think they're just the same, you could be making more with Yahoo but sometimes Adsense is just the most basic ad network our there that you just know you can't go wrong with them.
