I would recommend getting a more common gun like an M4. There are more accessories available for it and if it were to malfunction, there are plenty of people around who know how to fix it.
The dragon, however, does use the same gearbox so upgrading and maintaining it shouldn't be a problem, but it is a really big and clunky gun. You can't really add any other external accessories like scopes or flashlights... and even if you could add anything more to it, it would look absurd. The dragon, in my opinion, is a really ugly gun, but I can't stop you from getting one. At this point, it's all based on your preference.