Avantages
I honestly think SMS is trying to take care of their employees. They communicate with them and try to provide training and promotion opportunities. The market of government contracts is volatile. Having unexpected things happen to contracts is not unique to SMS. I think the merge with Lockheed Martin was a good move for stability going forward.
Inconvénients
However, I think SMS could be better at the political game. They seem to be blindsided by not winning or losing contracts more than they should. I don't know if there are problems with other contracts I was not a part that affect other projects or not. The quality of your work experience seems to be determined by who is the Project Manager. There is a wide range of experience and management styles in the PMs. It would be good to see that more consistent project to project.