Do you take most of your pictures indoors often? If yes then 17-55mm
Do you take most of your pictures outdoors? If yes then 15-85mm
I have both lenses and each of them has its own benefits. If outdoor I use 15-85mm for crispy clear landscape pictures with my family members in the pictures. I use 17-55m indoors with all my livingroom lights on so that I dont have to use flash light on my family members.
By the way, Sigma 50mm F1.4 is another great choice of your lense collection, I use Sigma 50mm f1.4 more than any lenses I have.