Hard to say without knowing what's most important for you. CPM isn't, but what is? Both are probably not going to really promote you, but Fullscreen seems to try harder to give you tools to help yourself. Like an app to post videos on Facebook (and still get ads/revenue) they were pretty fast in making an app for Google Glass and stuff like that. I'm not a Fullscreen partner, so I can't tell if their tools are any good, just that they are trying. So I would probably be leaning towards CreatorX.
But if you're unsure you can always throw a coin. And if you are unsatisfied with the result of your throw, then you'll know what you've secretly been wanting the whole time...