I couldn't resist falling back into the schoolmaster mode, so here we go:
Bailing vs fighting in bombers - An example from a score point of viewI randomly grabbed the actual bomber score of a top 50 ranked player:
14 sorties; 3 deaths total (including bail & captured); 690,448 damage points
Let's assume he makes another bombing run in a formation and gets the same average damage points for it as in his previous missions.
I calculated the impact on his score ratings for three different outcomes:

As you can see, the difference between bailing and getting shot down are minimal, but both have a huge impact on score in comparison to getting home. That's why it's always better to try to fight your way home, no matter how slim your chance is.