One of the reasons that there is generallly less waste and faster digestion with raw food than with kibble is because raw foods are about 75% water whereas kibble is about 10% moisture. So, on a weight equivalent basis there is more solid mass in kibble diets than in raw feeding. As others have stated the quality, form, and type of ingredients in raw food and kibble will also affect digestion rate. For example if you are feeding a raw diet that is high in bone adn vegetable content especially unground and even fur and skin then the digestion rate will be slow and in fact may pass through the alimentary system not only slowly but may be partially or fully undigested. If you are feeding a kibble with moderate protein levels 12-22% and high marginally digestible grain content like corn well then it too will not digest well at all and will pass slowly. The high protein content 32 to 40+% grain free kibbles seem to digest only slightly faster than regular kibbles. I can't explain it but from my experimenting with my own dogs and a couple of my friends who have trialed feeding the high protein content grain free kibbles with raw meat, the dogs seem to frequently have intestinal upsets and loose stools when the protein content gets much higher than 32 to 33%. I don't have an explanation for it especially when it is counterintuitive to the fact that raw meat with high water content is over 70% protein by weight when corrected to a dry weight basis. It just seems that the extrusion process and lack of moisture really in kibble affect digestion and absorption rates. This is only an anecdotal observation on my part. As far as raw food that is cooked and fed to dogs instead of actually being fed raw, I have not seen any difference in digestion rates or stool sizes. If you feed kibble with raw about 50/50 on a volume basis the digestion rates will be closer to the six or so hours people generally observe with BARF diets. The stool size will be slightly larger than barf stools but will not look like giant land mines like straight kibble diets. Hope this gives you some food for thought.