YPN targets ads for me, and it's making awesome... it doesn't target for lot of people if they don't choose right category:|
this is the million dollar question now isn't it. the truth is it varies per website/niche. of course with YPN you can force certain ads to appear, but still it varies per website/niche... you should test both and see which is better per website and/or page.
At the moment, I think YPN is a little better because they are trying to gain on adwords. But things are settling, and I think adwords may be the better long term bet.