Correct me if I'm wrong - ducking from incoming missiles - but do BA still retire at 55 and charter at 60? That for me would be a major factor. It won't mean you're are dead in the water (air) at 55 but you could have a choice of what to do, with hopefully enough funds to make a choice. At 55 in charter you would have no choice until 60 and then maybe not enough funds anyway.
All the other pro's & con's have been stated. The pension would be another major factor. I know BA's is now similar to everyone elses, but....
Fringe benefits in retirement is also a factor. Leave BA & you are still a member of the family; leave charter and it is as if you've never existed.