Pros
I am not aware of another company that has a better combination of leadership, culture, and mission-focused work. The people, from CEO all the way down to entry level engineers, are all bought into what we are doing, which can be described by our company mission statement: "Inspire Others, Deliver Value." I am excited to come into work (almost) everyday, I feel constantly pushed to be a better person/employee/engineer, and I feel a profound sense of pride and gratitude knowing that what we are doing has a direct impact for the men & women who serve our country.
Cons
Hardly any to speak of. There are some inherent trade-offs when choosing to work for a small company, but I think those are more than made up for by the leadership/work/opportunites/culture/etc.