Bell is very good at one thing. Defending the run. In today's NFL, even LBs must be able to cover. Having a safety who can't just doesn't make sense. Jenkins is on another level.
Let's not pretend that Bell is bad in pass defense. He's not. It seems like Saints fans are currently in the process of trying to convince that Bell is overrated. He's not...he's a very good SS and he's ascending. It's not inconceivable that he could be a significantly better players than Jenkins over the next few season. Jenkins is 32 years old.