Based on the traffic u get. Use all the best options and check which is converting well and use that.
I personally did not like adbrite and they charged me an extra fee when they should not have but I did get that cleared up in a day or two. But it seems like different people have different experiences with them. Good luck! (report back after you found something you like, if you don't mind )
From experience I can tell effortlessly nothing works equivalent to adsense. However you should try to monetize your site with relevant CPA ads and you may earn far better than adsense. Ultimately at the end of the day adsense advertisers too have to generate lead / sale out of your traffic. So if you can do that direct from your traffic, you will earn more.
there isnt a "best", there is only what is best for ur particular site and content. Try them all and see what is best for u and for ur site
Adbrite? That's not my experience. If you have adult content it's a good option with their Blacklabel Ads, but the return is small
adsense is the best but in case of the absence of adsense i think chitika is good.but the problem is that,it does not work well outside US and Canada.
Try CPMStar. If u want to see my progress here a sample, hope this high enough you expect to get. Aug. 1, 2012 - Aug. 31, 2012 Jan. 1, 2012 - Aug. 31, 2012