Adsense is the best choice for all the webmasters always work sincerely... that's a way that you can get success...
After a long run i do not think today's adsense giving more earnings.I dont know why yahoo is limited for US only.
well between any Ads publishing network, Google adsense is the best and serves most relevant ads to your audience and never runs out of ads inventory. Plus they charge the advertisers the highest rates industry and Shares around 68% of the revenue to users. which make it good for the publishers to get paid well. Well i will say , don't use Adbrite at all if you have a site which is fine with Adsense TOS, I personally used adbrite while i was not selecting in Adsense and they CTR and Paying rates are too low in Adbrite that it took me 6 months to reach $100, and they have sent me the check of my earning which never reached to me and no use of contacting their support. So try adbrite at your own risk.
I would go for adsense, just because they are older than yahoo in search marketing. I trust them more.
Yahoo has some great perks but overall adsense wins;hands down. Their more reputable and faster when it comes to payouts.