You should use Touch U.
Adobe is moving towards touch UI across marketing cloud solutions to provide an unified experience.
Adobe introduced a new touch-optimized UI with AEM 5.6 for the author environment. This differs considerably from the original classic UI as it is designed to operate on both touch and desktop devices. The basic principles of the touch-optimized UI are:
Mobile first (with desktop in mind)
Responsive design
Context relevant display
Reusable
Include embedded reference documentation
Include embedded tests
Bottom-up design to ensure these principles are applied to every element and component
Classic UI versus Touch UI
| ExtJS | Granite UI |
| Remote Procedure Call | State Transistions |
| Data transfer objects | Hypermedia |
| Client knows server internals | Client does not know internals |
| “Fat client” | “Thin client” |
| Specialized client libraries | Universal client libraries |
AEM is gradually migrating existing layouts/modules to Touch UI, but at the current point in time some UI’s are still on classic (original) UI (eg. design dialog). Adobe will continue supporting Classic UI in near future.
Please reed this full community article :- https://mkbansal.wordpress.com/2016/01/19/aem-touch-ui-what-and-why/
I hope this will help you.
Thanks and Regards
Kautuk Sahni