Pros
You have the chance to work on varying AAA IPs, due to the Ubi structure. Among the staff you will find very talented individuals with the passion to create great games. The idea of cultivating talent is supported up through management and helps create a great atmosphere of mentoring, learning and development. The culture is great and the employee retention is good. A game studio that has been around 15-20 years and has had only one round of layoffs, is hard to come by.
Cons
I'll be honest, Ubi style Co-Development can be challenging. But it is clear that the people who embrace it enjoy there work and contributions. Ubi keeps a pretty thought grasp on salaries, barely hitting market value. These two reasons are why some better talent ends up leaving.