I've been using dynamicnotications since it came out just after the Moto X and I like it better because it more closely simulates the Moto X. Also, I have a lot more control over the look and behavior, and can set it to breathe off after 6 seconds, then breathe back on every 30, or at whatever frequency I like. Knock is much less configurable regarding look and behavior.
Just tried knock and it's cool, very colorful (which might end up taking more battery) but def not the Moto X experience at all.
I'll stick with dynamic and see if he incorporates the laundry list of tweaks I suggested to make it even more like the Moto X.
Do we know if these apps truly use the battery-saving gains of not activating amoled black pixels?