Have to agree with FourGolds. Think about it, 777 deliveries continue at one to two a/c per month (despite a few delays due to vendor issues at Boeing). What is the fleet increase on the 'bus? The 380s will come at a snail's pace which will help to some degree and the 350 is still on the drawing board.
One other issue still not discussed is who is to fly the ordered 747-8s? If we get the nod, then of course it will be mostly Boeing guys.
And finally as others have said, I think the days off and and over all roster satisfaction is better on the Boeing. But the ULR flts will get to you after awhile on the 777. And you didn't mention what you have been flying, Boeing or 'bus or neither. I would say, stay with your current manufactuer unless its something else.