Pros: like feeding a fresh heart only that it's liked by everyone.
Cons: like human nutrition, the best things are more costly but worth it in the long run.
There is actually a variety of hearts, all equally loved by the 5 test subjects: chicken, turkey, duck. They are what gives me peace of mind that Grisou gets his share of taurine when he's in one of his moods that he eats baby animals only (who don't have much taurine). They get inhaled. Rascal couldn't eat them at first because his chewing muscles were underdeveloped due to being addicted to canned food, so he worked at them until he could eat those treats... now they help clean his teeth.
They can be crumpled onto new food as teaser. In fact, they also work as appetite stimulant, getting a cat into eating mode so after the treat is eaten, he'll turn to his bowl.
The only con is of course the cost. But probably saved vet visits could be factored in here by having a healthy cat.