Security features
In app editing is a feature that a lot of people don't consider when selecting these type of tools. It's something that Box and DropBox are unable to provide, relying on other 3rd party apps that have in built connectors to other cloud services, unless secure versions from Good or MobileIron are used. Accellion have been providing this in app editing function since last year.
The other security features that should be standard in these enterprise apps is app based encryption at rest on the device without relying on device encryption, and the ability to remote wipe the locally held, offline files from the app, both of which the Accellion solution provides.