It's well established that carnivores have much shorter intestinal tracts. Meat is relatively easy to digest and simply doesn't need a long break down and absorption process. So we know meat eaters don't need long intestines like herbivores.

Now, as to your question about long intestines making it harder to digest meat. They don't do that in exclusion, they make living at all more difficult, and digesting meat is a sub task of living. Research a bit on all the digestive troubles of horses and cows, colic and the like, and you'll find out that massive, long systems of intestines and stomachs have a lot that can go wrong and kill the animal.

Long intestines let the animal live off easier to catch food, yes, but there are definite drawbacks.