All publisher networks are different. It rather depends on your site and the visitors you get. But in general as an advertiser, Yahoo search m. charges way too much in comparison to adwords, so i would say they should be paying a bit more. On the other hand Y has less advertisers, so they might as well put more money in their pockets. Who knows.
YPN ads are not well-targeted so you'll get less clicks. Less clicks means less money. Payout is about similar.
in generally, it depends on what kind of site you're talking about. Personally, i think it's about the same thing, only adsense pays more money
YPN doesn't offer Link Units, which convert very well for me. They also have a lot less competition for the ads, so the ads will repeat a lot and not give you a good variety of ads. Well that's true for my niche any way. There may be some niches that have more ads. I've found that the quality of the copy of the ads is very poor on YPN too. The CTR is much lower. Again that may just be in my niche. The one upside is that they usually paid a lot more per click than Adsense. Actually I'm not sure about that anymore. I haven't really posted YPN ads for about a year because they were converting so poorly. I just recently set up a new site using YPN ads, but in a very different niche than my other sites.