Interstitials are the most profitable and user friendly ads (because you don't have to put ugly banners everywhere in your layout), however, as I said:
AdMob interstitials on XDK = ok
AdMob interstitials on MoPub/CocoonJS = tragedy
My friend has 3$ / eCPM for native AdMob interstitials,
I have terrible low fill rate for AdMob interstitials on MoPub
and funny US$0.80 eCPM (which is worse than banners).
However my app won't run on Chromium (XDK)
and even if - Canvas+ is still much faster