I totally agree with Matt. "Layer" feed provides what is necessary to produce eggs, but the rest of the bird might not look that great. The only thing that it provides "better" than a regular feed is calcium. However, most companies do recommend that free choice oyster shells be provided in addition to their layer feed, so that extra calcium really isn't critical if you're also giving oyster shells. The only advantage is that the hens cannot avoid the extra calcium in layer diets, so a hen that might not like oyster shells will still get extra calcium, which it may or may not need.
Years ago I had a beloved pet hen with a lot of medical problems. She was highly monitored by her avian veterinary specialist, and because of her issues she couldn't eat any of the commercial diets, and she couldn't have excessive calcium in her diet. She was put on a homemade diet using specific grains, fruits, vegetables, fish, etc, balanced by a nutritionist to provide maximum health. Again, this was not a high calcium diet. She laid perfect eggs with beautiful hard shells, around 200 her first year, about 180 her second year, about 100 her third year, about 20 her forth year, and only 3 her fifth year. She enjoyed an excellent quality of life, and her body condition and plumage were perfect. She started to show her age in her sixth year, and died at 6 years, 10 months old. Not exactly geriatric for a good quality heritage breed, but Sydney was a commercial broiler hen, a meat hybrid that rarely lives beyond 18 months when kept as a pet.
She provides a good example of how a bird with excellent nutrition doesn't need "layer feed" to produce eggs. Now, I don't monitor my flocks to that level, and I don't custom mix a homemade diet for every individual bird based on professional physical exams and frequent blood tests, adjusting the nutrients as needed based on those results. That's just impossible, and totally unnecessary for healthy animals. For my flocks I provide a mix of different commercial diets: one alfalfa based, one soy based (a game bird layer diet), and one fish based, all mixed together, plus veggies and fruit from the garden, fruit from the orchard, extra milk from the goat, fish scraps when available, free choice oyster shells, and a large pasture with adjoining forest area to free range. They look great, and they produce large numbers of eggs for many years (my 8 year old Croad Langshans are still laying -- not often, about 10-12 this year, and no longer fertile, as the rooster is arthritic and breeding is a bit of a slip-and-slide, but they are quite elderly birds for the breed and any production is above and beyond at this point). They eat a lot of grass, which balances out the high protein of the milk and fish, and it all seems to work well. Plus, the culls taste amazing with a flavor that is never bland, and provide better nutrition to the person who eats them (in the long run, what you feed your prey is ultimately what you feed your predator, whether you're raising mealworms to feed your birds, mice to feed a snake, or chickens to feed a person). There's so many options for a feeding plan. The single bag method is no doubt the easiest, but if you train yourself to evaluate their body condition and production, and are willing to use multiple products, you can definitely move your feeding program, and your results, up to a higher level.