We often have clients who want a app that functions via the web and as a mobile app as well. They want these styled similarly, drawing on the same data.
We are experienced with Angular and it would be great to be able to use Angular to deliver the views in web and on mobile. And it would be a timesaver to have the same sass framework set the styling on all devices.
Plus we are primarily a web shop and using Angular plus Ionic would allow us to deliver mobile apps as well as web apps.
Regarding the backend, Node/Mongo is my preferred server side infrastructure and I want to move us away from PHP/Apache for most of our projects.
Those are the benefits of a MEAN + Ionic integration.