6d +24-105l is better. Had both combos. Even though the L is only f/4 it will have similar or thinner depth of field on the 6d than the 17-55 2.8 on a crop. FF vs crop at similar focal lengths has about 1 1/3 stops diff in DoF. Plus the focal range is better too. Nicer portraits, wider landscapes. Also, the 6d is well more than a stop (close to 2) better at high isos than the 60d, so that more than makes up for the 1 stop smaller aperture. Buy it, do it, you won't regret it. I never hesitate to use mine wide open.