I'm a huge believer in dry kibble, because hard foods have been shown to stimulate the gums, and help prevent gingivitis, which is a large cause of tooth loss in dogs. I've seen over the years the difference in dog's teeth who have only had kibble, and from this experience alone, I believe it's better, however there is scientific data to back this up. See for more information:
THE EFFECT OF HARD AND SOFT DIETS ON THE GINGIVAL TISSUES OF DOGS -- BURWASSER and HILL 18 (4): 389 -- Journal of Dental Research