Experimentation and context-oriented-rotation are the 2 keys to unlock greater AdSense amount. What works for 'A' doesn't necessarily work for 'B' and vice-versa.
CPM isn't everything. Someone with a relatively low CPM and high traffic can do just as well as someone with a high CPM and low traffic (granted their CTR is about the same). CTR is very important to me and sometimes minor tweaks in your ads or websites can really make a difference.