I have been using StartApp for 1.5 years more or less with INTERSTITIALS. They pay really well but since 2-3 months ago ecpm has fallen a lot. My ECPM has always between 4$-4.5$ and the average now is about 3$ having days with ECPM of 2$. I want to move to another network and has been thinking about admob. Could anyboy give advice on this? I'm using banners with them and they are working pretty nice but don't know about Interstitials. I talked with a google assistant and he commented that they had 4$ ECPM interstitials as an average. What do you think?

Thank sin advance.