Hill's Science Diet Adult chicken is positioned around balanced nutrition and a clinical-nutrition background, a steady long-term everyday diet. Royal Canin I27 focuses on the indoor lifestyle, using moderate calories plus a fibre blend for body condition, hairballs and stool odour.

Both target adult cats over one year. Hill's suits households without special concerns that want a stable formula; I27 suits long-term indoor cats with low activity, post-neuter gain or occasional hairballs, where the functional target is clearer.

I27 concentrates its claims, but an active cat may not need extra fibre design. Hill's is balanced yet has no obvious indoor hook, and its reference price is not low. Both are mainstream formulas, and kibble size and palatability vary by cat.

First judge whether the cat has a weight or hairball issue: if so, favour the formula with a clear target; if not, pick the stable, easy-to-restock option. Transition over seven days. Persistent weight gain or frequent hairballs warrants a vet check for skin or digestive disease.