Pros
A stable, slightly less than market income. A gym. "A good payout to your spouse and kids if you die at work". (An actual quote from a worker there).
Cons
If you love making great software - don't work at Citi. They are a technology company who will figure out they are a technology company right when their market is taken away by competitors who offer a better user experience, higher-quality software and a caring and inclusive culture for their staff. The software development model is Waterfall in drag as Agile, design principles are driven by daddy-knows-best and successful output is measured by adherence to outdated requirements and principles. It may be the case that user lock-in is enough to keep the behemoth alive..but if you want to work in a place where people swallow pills to keep going, have cardiac arrests at work and in which gratitude for a job is supposed to be enough to overlook the glaring organisational flaws - then it may be the place for you.