I have to say cabas. I tried both, too, and the cerf just didn't fit. I couldn't keep it over my shoulder, but the cabas was perfect. I would say function over form, but I really like the look of the cabas, too
It probably would depend on what will fit your lifestyle better -- if you are looking for a bag for work, i'd go with cerf, but if you are looking for a more casual bag, i would pick the black baby cabas!