Canned food is much healthier for cats than dry food. It contains high protein levels, which our carnivorous kitty companions NEED for proper muscle mass, weight, and gut health. Canned food also contains high moisture levels, crucial for our cats who, like many species imported from the desert, don't have a strong behavioral drive to drink enough water to compensate for a dehydrated dry diet.
Canned food may also be better for the teeth, as dry diets contain a lot of carbohydrate (sugar) that tends to stick to the teeth when chewed, promoting plaque and tartar development. Feeding an exclusively canned food diet from kittenhood instills good dietary habits--dry food, like most junk food, is tasty and addictive! It can be difficult to convince a cat who was raised on dry food to switch to a healthier canned food diet.
Start your kitten on a healthy diet early--pick a canned food that is pate style (not drowning in "gravy," which is flavored high fructose corn syrup, not healthy for any of us!), and preferably poultry rather than fish or beef. Poultry-based foods are more natural for cats than fish or beef, neither of which cats are adapted to eat. However, a cat on a canned fish- or beef-based diet is still much better off than a kitty eating dry food! By feeding a canned food diet, you will protect your kitten from developing obesity, diabetes, urinary issues, skin and coat problems, and gastrointestinal issues.