There's a Reddit AMA being conducted by Masa Tanaka, creator of Onsen UI and Monaca tools. It touches on some high-level topics like the future of hybrid app development and the business model for a free, open source tool like Onsen UI. Tanaka sees hybrid mobile app development opening up mobile development to more people.
"I'm sure hybrid apps is a huge driving force for those who couldn't access to mobile app development, because of its complexity and difficulty to support various mobile platforms."
And, yes, Tanaka touches on Onsen Versus Ionic, probably to two most well-known HTML5 hybrid mobile app frameworks.
"Onsen UI is similar to Ionic since both are UI frameworks and targeting for mobile hybrid and web apps. However, Onsen UI 2 and Ionic are different in the way providing UI components.
We try to be JS framework agnostic, so Onsen UI is implemented using Web Components (Custom Elements). That makes us room to support many popular JS frameworks, including Angular 1, 2, React, Vue.js, jQuery and many others. Ionic supports Angular 2, which is one of the most popular frameworks for Cordova and the web.
We've seen many people using Onsen UI and actively contributing to the community these days. That's awesome, but we are not as famous as Ionic. I hope you give Onsen UI a try and see if it does good job for you."