Is it more efficient from an energy standpoint to be a vegetarian vs. an omnivore?

Evolution dictates our lot in life with the undisputable fact that in order to survive, all animals, including us, must consume the by-products of DNA (i.e., living things). Since living things provide the only DNA sources available, we must eat the flesh of life (plants and/or animals) to continue our existence. This presents a dilemma and a moral problem if we consider killing life as immoral and conserving life as moral. I hope to clarify some of the problems and to dispel some of the myths about eating plants and animals both from a health and moral perspective. We can have no argument about the following: all animals consume either plants, animals or both. Every species of animal falls into the category of either carnivore, herbivore, or omnivore (other classifications exist such as frugivore, granivore, insectivore, etc. but these fall under sub-classes of the three major groups). Eating high concentrations of protein (meat) has evolutionary benefits for carnivores. Meat serves as an efficient way to build a body and to economically replenish lost muscle tissue. Carnivores usually have lean, fast moving bodies, good for running down or overpowering prey. They have short digestive tracts, good for quickly eliminating unnecessary mass and allowing a high muscle, low-fat balance. Humans do not fall into the carnivore group. Herbivores (vegetarians), on the other hand, need longer intestines to break down and assimilate tough-to-break-down plant fibers. This means that the food stays in the gut for long periods of time. Most herbivore mammals have higher fat concentrations than carnivores and they don't have the speed compared to carnivores. Just observe the large bellies of the great apes, and ruminants (oxen, cattle, sheep, etc.), and you will see how obese they seem compared to hunter-carnivores. Humans do not fall into the herbivore group either. Homo sapiens, of course, fall into to the omnivore class. Through natural selection, we evolved the teeth of omnivores, good for grinding grain, stripping leaves, and eating meat. We have long intestines (somewhere between carnivore and herbivore intestinal tracts), and a digestive system that will break down both acidic and alkaline based foods (protein, carbohydrates, and fat). Our closest relatives, the chimpanzees, also have an omnivore diet (not only do they eat plants and fruits but they hunt and eat monkeys, for example). Humans beat all other omnivores by a large margin (omnivore comes from the Latin: Omni or everything). People will eat anything including bacteria, fungus, plants, and animals. From the plants, we will eat roots, bark, sap, leaves, berries, fruits, nuts, flowers, and seeds. We will eat any animal, including worms, insects, crustaceans, fish, amphibians, reptiles, birds, and mammals (and in some cases, people). We will eat their meat, fat, eyes, brain, organs (including testicles), bones and shells (for calcium), milk, and blood. Humans will even eat rotten food such as cheese and sour cream (due to decomposition from bacteria). Risen bread and alcohol drinks made by fermentation comes about from the waste products of yeast. Japanese people eat natto, a form of rotten fermented soybean. Ræst kjøt comes from rotten mutton. Humans eat lots of rotten fish. The Icelandic delicacy hákarl comes from a rotten shark; the Swedes love surströmming, a rotten herring dish; Ræstur Fisker describes a half-dried rotten fish delicacy; the Russian Fresca comes from decomposed codfish. Some humans even drink urine. Yes, urine*.