If this came about, the gumph about saving animals is irrelevant since nearly all cows, sheep, pigs etc exist purely to be farmed. So with no purpose, they would be killed off. I don't think it would produce as good a quality meat as you get from a real animal, which is already not that great since they're fed to grow fast, leading to fatty and blander meat in my opinion. Nutrition wise, you could squirt as much added nutrients into it as you like, I do wonder if this lab grown meat would have the nutritional value that animal meat would have.