I have went through several CPM based networks and most of them allow animated gifs or flash swf's. That makes me wondering who would use static banners in these networks? What would be the benefit of it if you are buying on CPM basis? It's obvious that you will get higher CTR from animated ads. Or am I wrong?
Wrong.
Animated ads don't always outperform static ads and SWFs are incompatible with iOS due to Flash support.
In media buying it's the same i.e. on desktop traffic you can't be sure an animated banner version will do better than the static equivalent.
It's something you would test on a per-campaign basis.
For some verticals animation might inevitably do better e.g. adult.
In previous tests I've had static ads destroy animated ads because they look less like ads. Like Zeno said it's a case by case basis, you have to test both.