Norwegian Forest Cat vs Siberian

This breed is marketed as a hardy, naturally-evolved landrace with few health problems, which is true for most individuals, but it carries a rare fatal metabolic disease that kills affected kittens in infancy or early kittenhood, and Cornell's feline health center also lists it among breeds with elevated hypertrophic cardiomyopathy risk — a DNA test exists for the fatal condition and there is no excuse for a breeder not to use it.

Siberians are marketed as 'hypoallergenic,' but no cat breed is allergen-free — every cat produces the Fel d 1 protein that triggers allergic reactions, and while research suggests roughly half of Siberians produce somewhat less of it than average (about a fifth produce notably little), the rest do not, so the only reliable way to know if a specific cat works for an allergic person is to spend real time with that individual cat first.