American Shorthair vs Birman

The 'all-American working cat' story implies a hardy, mixed-heritage constitution, but this is a closed pedigree bred like any other purebred, and Cornell's feline health center lists American Shorthair among the breeds with an elevated rate of hypertrophic cardiomyopathy — the same silent heart disease people specifically worry about in Maine Coons.

Birmans are marketed as a calm, especially healthy longhaired breed, but they carry a distinctly higher-than-average rate of blood type B (and the rare AB type) than most cats — which matters enormously in an emergency transfusion (there is no universal donor blood type in cats) and can cause fatal newborn kitten losses if a type-B queen is bred to a type-A tom without testing first.