Short answer — vets most commonly recommend brands that are research-backed, have complete-and-balanced formulations (and veterinary/prescription lines for medical problems). The brands you’ll hear most often are:

• Hill’s (Science Diet for general feeding; Hill’s Prescription Diet for medical conditions). (petmd.com)
• Royal Canin (Feline Health Nutrition + Royal Canin Veterinary Diets). (vcahospitals.com)
• Purina (Purina Pro Plan and Purina Pro Plan / Purina Veterinary Diets; Purina ONE is also commonly used). (petmd.com)
• Iams / Eukanuba (commonly recommended, especially for routine, budget‑friendly complete diets). (petmd.com)
• A few premium/natural lines vets will also use or discuss depending on the patient: Wellness, Nutro, Merrick, Orijen/Acana (Champion Petfoods) and some regionally available brands. These are less uniformly “vet‑recommended” but are commonly mentioned by clinicians when the formula suits the cat’s needs. (cats.com)

Key points vets use when recommending a brand (why you’ll see those names mentioned):

• For sick or special‑needs cats vets often prescribe a veterinary (prescription) diet because those formulas are developed and tested for specific conditions (kidney, urinary, gastrointestinal, food‑allergy, weight management). (vcahospitals.com)
• Good veterinary advice focuses on complete-and-balanced diets and evidence (feeding trials / nutrient guarantees) rather than marketing buzzwords — look for the nutritional adequacy statement and clinical/trial support. (vet.cornell.edu)
• In Australia (and elsewhere) animal‑welfare and veterinary bodies recommend a high‑quality commercial food appropriate for life stage/health; your local vet or RSPCA will prioritise a diet matched to the individual cat. (rspcansw.org.au)

Quick practical tips

• If your cat is healthy, pick a reputable, complete commercial food appropriate for life stage; consistency matters more than brand‑hopping. (vet.cornell.edu)
• For medical problems (urinary disease, kidney disease, food‑responsive skin/gut disease, obesity) follow your vet’s prescription or specific brand/formula recommendation. (vcahospitals.com)
• If you want a second opinion on a particular brand or formula, bring the product label (or ingredients/nutrient panel) to your vet — they’ll check suitability for your cat’s age, weight and health. (vet.cornell.edu)

If you’d like, I can:

• give a short pros/cons comparison of 2–4 specific brands you’re considering, or
• check availability of particular veterinary/prescription diets in Australia.