All of the iguana species I can think of are herbivores, so they go with the cows. 
Geckoes are mostly predators.
Pigs, and long pig, are omnivores… but apparently still manage to be tasty when done right.
Herbivores also tend to pile on the fat when the feeding is good, which makes for juicy food. Predators who get fat have trouble eating, or at least catching dinner. There’s a lot of non-predators that are an acquired taste. Moose can be gamey, even if it is butchered right. Even mutton has a distinctive taste some may not like. For many game animals, you have to be careful not to cut the anal glands or else the smell goes into the meat.
Perhaps we have chosen our foodstuffs over the millennia simply because the taste is not unappealing - i.e. lobster taste better than slugs, so we like it. Also, evolutionary-speaking, predators will tend to collect the diseases and contamination of their prey so such food is probably not appealing because we recognize it is less healthy.
The eyes in front thing depends on the application. Herbivores in the trees and jumping from tree to tree need spatial judgement (which is how we ended up with binocular vision) while animals on the plains that run from predators prefer a good head start and so good close-to-360 vision. Birds OTOH, no matter whether they’re hunting seeds, worms, or other birds, need really good all-around vision - probably a safety issue when flying. However, a predator like a wolf probably does not have to be as concerned with what’s behind him because the risks are minimal, very few things attack a wolf.
I just want to point out that this is biology. Therefore, any rules that anyone comes up with are going to be no more than vague guidelines. If you look hard enough, you can find an exception to any rule in biology.
Size comes to mind. Only herbivores can grow to sizes like the Elephant or the Whale where they can afford to be slow.
Meh. The Blue Whale is a carnivore (almost an insectivore, so to speak). And Tyrannosaurus Rex weighed roughly the same as the largest elephants.
Being General Questions, the ignorance exhibited above must be fought. Rumours of foul-tasting wolves and gristly bear steaks abound, but practical experience tells otherwise. Many predators are extremely tasty, many prey animals less so. I’ve personally eaten and relinquished choice meat animals such as fox and bear, and know people who swear by lynx meat as the best meat out there. I’d rate fox meat as equal to the best pork one can find. Bear is different, but extremely good eatin’. Alas, lynx is a rarity, I have no doubt about it’s excellence.
You have it backwards. Meat animals are grain-fed because it’s the only economic way to feed them, not because grain is needed to make the meat palatable. This is the reason semi-omnivorous dogs, and not tigers, are bred for food. Raising meat on meat is utterly uneconomical, the more so the bigger the animal. Also, predator meat (bear) is available in Western super markets, at a premium price, as is bear meat in high-end restaurants.
Many prey (herbivorous) animals have such harsh diets that their meat is very gamy, but eating meat does not render meat unpalatable, like eating tree-bark does. Grain-fed deer tastes ‘better’ (=milder) than wild-foraging deer, but a meat-eating animal tastes as good, as meat, like grain, is mild food itself, free of tannins and extractives and repellants.
I suspect us Westerners find eating predators improper because we equate eating predators with cannibalism, to an extent - we’re not supposed to eat those who eat others. Many indigenous cultures included many predator animals in their diet. The Saami, for instance, considered fox, marten, badger and bear as food animals, just like many Native American societies did. But no indigenous culture that I know of ate every animal out there, so it was not a question of avoiding starvation. There always were food taboos, they were just different from ours. Cultural bias explains why Michigan hunters avoid predator meat. It has nothing to do with the physical differences between prey and predators.
It’s not hard, it just doesn’t make economic sense. You have to pay for grain to feed the rats and pay for rats to feed the snakes. From an economic standpoint, vegetable protein makes the most sense, but eating those that eat vegetable protein is so damn yummy and delicious we don’t mind one intermediate step of expense. And of course there *are *exotic meat butchers who do offer snake, but pound for pound it’s *much *more expensive than pork chops or hamburger.
Do you mean predator in that first sentence? I thought prey animals are what we eat, cows etc. are bears, wolves predators?
Some predator animals do not have well developed systems to handle toxins and have relatively poor liver function.
Cats and their ilk are not very good at handling fairly mild toxins, they rely on their prey to filter out all those nasties.