Pros
One of the only truly global defence companies - with opportunities to work almost anywhere in the world at senior level. Good products and range in their sector. Some exceptional engineering and scientific skills. I always tell people you don't get to be awarded a Nobel Prize for Physics (Albert Fert) without some strong skills ! Not an American strong arm business. Honest, committed people. Good benefits and generally fair treatment of people (perhaps soft). Positive culture - though it is hard to get your head around as its Franco-centric (they write the rules) Reasonable investment in training.
Cons
All roads lead to Paris. French approaches to business don't always export well. Control structures can be impenetrable and confusing. Generally poor commercial awareness. Pay is not the best (slightly compensated by other benefits if you stick around). UK lacks the engineering discipline of the French.