I am frequently asked whether or not cats should be fed dry food (kibble) only, or canned food in addition to kibble. My answer in the case of normal, healthy cats is dry food only, with the caveat that it be a top quality dry food.
Poorly formulated dry food often contains fish meal of various types, always a no-no unless it's medically unavoidable, and also can have too much plant protein in proportion to animal protein. Fish sets the cat up for skin, urinary, and gastrointestinal problems (which can be dangerous and not merely annoying), and too much plant protein makes for urine that is too alkaline (can set up more urinary problems).
Canned food has its own inherent problems. It can lead to far too many vomiting and diarrhea complaints, leads to excessive dental problems (if you eat mush you get "mush mouth"), is a very expensive way to get calories into your cat, and has been linked to risk of hyperthyroidism.
There may be circumstances in your cat's life that call for canned food as part of a medical management plan, but for everyday feeding a well-chosen and top quality kibble is just fine. And in the majority of cases, free-feeding is acceptable.
