As always with any question that asks for "the best", it depends. What's you blog about? What kind of traffic do you get? In what demographics? What kind of behaviour do your visitors show when they land on your site? Where do you get your traffic?
For example, a site with a high throughput of visitors who bounce quickly is often better off with a CPM offering - your traffic lands (registering a view of an ad), stops for 10 seconds and leaves, but you've earned your cash. By contrast, a site with a low throughput of visitors who stay on-site to read several articles is often better off with a CPC offering or affiliate marketing (depending on the blog's focus) - your traffic lands, stops for a while to read and may see an ad that interests them... click. You've earned your cash.
There is no "best" except the best for your situation. As far as networks go, they're all pretty much the same in the end - most CPMs pay similar rates, most CPCs pay similar rates, most hybrids pay similar rates, and so on. AdSense is generally best if you're going CPC because most of the others just farm AdSense out to their subscribers and skim a percentage off the top.
