For a good traffic getting sites the best ads serving option that I am suggesting is CPC. Because if a site is able to generate 1000 to 3000 visitors a day then there is a possibility to get at least 35 clicks a day by considering a ratio as 1:100, sometime even more clicks may recieves. Mainly the CPC ad network give pays to the clicks depending of the geo targetted. CPC ads publishing is profitable if the sites gets ads click if not it is bad day to the webmaster. There is more chance to get text ads than graphical ads and also text ads are seo friendly so that it reduces the loading time of a site rather than the graphical ads. It is best to choose both CPM and CPC providing ad network so that the webmaster can double their earnings. Some ad networks like google adsense, chitika, clicksor are serves both CPM and CPC ads in a website while adhitz, adclickmedia etc serves CPC ads only with good rates. The ads of adhitz are graphically good which help the webmasters to recieves more ads click. Using CPC and CPM ads in low traffic getting site is bad option that the sites recieves only few traffic so that it is very difficult to get ads click or to generate 1000 views a day.
For that it is best to choose CPV ads, in the case of CPC getting more clicks is depend on the skill of the webmaster. It is not easy to turn the whole traffic into clicks but it is possible to get some clicks from the traffic. If a site has huge number of traffic then it is possible to get more clicks. And also for this kind of sites all ad networks are workable. From some of the adhitz stats I had noted that a site having 26000 pageviews day has able to make 3000 clicks which results in making 82$ in a day. I doesn't believe it in the beginning before I saw the adhitz stats image of the site. So using ad network in a site is profitable when the choice and skill of the webmaster. All the best.