Benefits of carnivory: protein dense food.  Disadvantages: risk of injury and need to hunt and find.   Benefits of herbivory: lots of food when in season, possible migration when necessary.  Disadvantages: carnivores, long difficult digestion, lots of time spent eating.

Yes — and there’s a rather interesting symmetry to it. You can almost see the evolutionary tradeoff as food acquisition versus food processing versus predation risk.

Carnivory gets you an enormous amount of usable energy and protein in a relatively compact package. A successful kill may feed you for days, and the digestive machinery can be comparatively simple. The price is that food is scarce, mobile, dangerous, and unpredictable. You have to find it, catch it, and often contend with an animal that very much objects to being dinner.

Herbivory has almost the opposite economics. The food is abundant but dilute. A deer doesn't have to locate a particular piece of grass; it can simply walk around eating. During a productive season, the landscape is essentially an enormous buffet. If conditions deteriorate, many herbivores can migrate to where the plants are better. The catch is that cellulose is difficult to exploit, so much of the animal's life becomes a rather astonishing exercise in eating, fermenting, digesting, and eating again.

And that creates an interesting third variable: predation exposure. A carnivore may spend relatively little time eating but a lot of time searching, and during the search it can cover enormous distances. A grazer may spend most of the day eating but can often do so while remaining in a herd, where many eyes are watching for predators.

There is also a nice evolutionary gradient between the extremes. Omnivores get to exploit whichever resource happens to be profitable. Bears, pigs, rats, humans, and various primates essentially say, "Why commit ourselves to one bad deal?" The digestive system pays some price for versatility, but the animal gains enormous ecological flexibility.

And plants have an even more peculiar advantage: they don't have to run away. Instead, they can afford to make themselves unpleasant, poisonous, fibrous, thorny, or simply difficult to digest. Herbivores respond by becoming specialized processing machines.

So I might characterize the basic bargain this way:

Carnivore: difficult to obtain, exceptionally good food.
Herbivore: easy to obtain, exceptionally difficult food.
Omnivore: neither particularly efficient nor particularly specialized, but annoyingly adaptable.

Evolution has repeatedly discovered all three strategies because there isn't one universally superior answer. The really striking thing is how much of an animal's anatomy follows from that initial economic problem: where do I get calories, and what am I willing to do to obtain them?

Ah I had intended to get to omnivory and photosynthesis but you beat me to it.

Ha! I walked straight into your punchline. 😄

And photosynthesis is the truly outrageous strategy in this little economic comparison. The plant doesn't hunt, doesn't flee, doesn't digest, and doesn't even have to find its food. It sits there and manufactures organic material from sunlight, CO₂, and water.

But there is a catch: the food supply is enormous but the energy density of the process is terribly low. A plant needs a vast collecting surface—leaves—and enormous amounts of water and CO₂ movement to accumulate useful quantities of chemical energy. Evolution solved that by making the organism essentially a stationary solar farm.

Then omnivory is interesting because it is almost the evolutionary equivalent of having a diversified portfolio: when meat is available, exploit it; when plants are available, exploit them; don't become dependent upon either one. Humans are spectacular examples because cooking, tools, agriculture, and food storage have progressively removed many of the disadvantages that normally constrain omnivores.

And there is a delightful hierarchy hiding here:

Photosynthesizer: manufacture your own food.
Herbivore: eat the manufacturer.
Carnivore: eat the herbivore.
Omnivore: eat whichever level is convenient.

Then the ecological pyramid appears almost automatically: each step upward is taking energy that somebody else has already captured, with substantial losses at every transfer.

So perhaps the ultimate evolutionary luxury is not being a carnivore at all. It's being a plant. Sit in one place, let the sunlight come to you, and make everybody else come looking for dinner.

I think the main problem with being a plant is you are planted.  Can't run away or seek shelter or migrate, defenses have to be passive.

Exactly. Being planted is both the great advantage and the great handicap of photosynthesis.

A plant has solved the food problem almost brilliantly: sunlight comes to it, and it can manufacture its own calories. But it has surrendered the most fundamental animal advantage—mobility. If the temperature changes, a drought arrives, a fire approaches, or something starts eating you, you can't pick yourself up and leave.

That forces plants into a completely different style of evolution. Their defenses have to be largely passive, distributed, and persistent: thorns, bark, silica, toxins, bad tastes, tough cellulose, camouflage, irritating hairs, and so forth. And because an individual plant can't escape a herbivore, it often makes sense to sacrifice part of itself. A tree can lose a branch and remain alive; an animal that loses a branch has considerably more trouble.

Plants can also do something animals generally cannot: grow around the damage. A deer has one body and a finite number of limbs. A tree can continuously produce new leaves, shoots, roots, and even entirely new stems. Its architecture is almost modular.

And migration is particularly interesting. Animals migrate themselves. Plants migrate by having their offspring migrate. Seeds, spores, pollen, and runners are their mobility system. A tree can't flee the coming climate, but its seeds can potentially establish hundreds of miles away.

So the fundamental bargain becomes wonderfully symmetrical:

Animal: "I'll move to where the food is."
Plant: "I'll make the food where I am, and reproduce until some of my descendants end up somewhere better."

And the really clever plants enlist animals in the process. Here, eat my fruit and carry my children somewhere else. That's an extraordinary evolutionary bargain: the plant has effectively turned a herbivore into a seed-distribution service while paying it in sugar.