The banner module as far as I can see serves the same size images whatever the screen size.
This means a lot of waste bandwidth on small devices.
Foundation has a tool that requests content based on screen size:
http://foundation.zurb.com/sites/docs/interchange.html
This is different from just using classes to show or hide content as the content isn't requested at all with Interchange.
Is there any plans to introduce something like this in the module?