Vantaggi
If you get the right team, you'll be working with modern tools and encouraged to contribute to inner source. Supportive environment. A lot of access to continuing education, volunteering, and benefits. Clear boundaries and responsibilities, energetic environment. Very technically capable employees (collaborative growth). Good pay. Internal mobility is now encouraged.
Svantaggi
If you get a bad team, or a bad legacy project, it can be a horrible experience. I've seen several talented engineers get frustrated at the lack of impetus to improve existing systems. Business often bleeds its responsibilities into engineering, leading to rushed projects or bad decisions because non-engineers are driving the conversation. A lot of internal forks of third party projects or dated Bloomberg implementations of existing tech (related to the above, fortunately changing). Normal trappings of internal politics expected of large organizations.