How do they compare to rabbits?
Well.... first GPs need vitamin c their only real draw back. but lots of ways to ensure they have this, including tables scraps. sprouts. dried fruits or rose hips, or berries etc.....
Now with that in mind, rabbits CAN eat as low maintenance of a diet as GPs. besides the vit. c grass is fine if that all you have. weeds from around the yard. You could easily have them in cages that let the grasses in and move them around the lawn.
rabbits will eat all the same things, BUT rabbits raised for tasty meat need grains as I understand it. they will be rather rough in the taste department otherwise..... GPs taste good even on that type of diet.....
then comparing the quality of the meat. my grandma ate them once, she loved GPs and doesnt care for, fat farm raised rabbits. By ALL accounts GPs are very tasty. I love rabbits to myself...
nutritionally though rabbit meat is lacking. from survival books Ive read, surviving on rabbits for protein alone isnt good, and you need to suck the marrow out of the bones. I forget which things nutritionally rabbits lacks.... but GPs on the other hand... are far superior to beef and mutton and all the more common animals. they have higher protein and lower fat. a good range of the other key things we need from meats...
you can also raise them in much closer quarters safely.
so basically, they are healthier, tastier, and easier. Only drawback being vitamin C.....