Is Docker right for my use case?

So my company has a system we sell that consists of basically a mini-computer “Smartbox” that is running Ubuntu 12.04. This box runs a Django application plus a number of different upstart processes related to it. Not much else. We have thousands of these boxes out on the field. We manage the package dependencies, process registration, etc. through a deb package with varying degrees of success.

We need a way to efficiently and robustly push updates out to our users out in the field. We also need something that as we upgrade the OS (we are way overdue for a Ubuntu upgrade as you can tell) we can feel relatively secure about our packages “just working”.

I don’t know much about Docker, but when I first heard about our problem (I’m a new hire), Docker was my first thought. But the more I thought about it I felt like maybe it wasn’t, as these boxes are ours we control the OS on it which is a big part of the value proposition of Docker, or so I understand. So if we KNOW our boxes will always be Ubuntu and we basically just have a Django app plus some processes to run, is Docker any better than a deb package?

TL;DR: Docker vs deb packages for a distributed appliance that will always run Ubuntu so platform independence is not that important.