Cavalier King Charles Spaniel vs Pomeranian

Heart disease isn't a risk for Cavaliers so much as a near-certainty — about half develop a heart murmur from mitral valve disease by age 5, and veterinary sources note that essentially every Cavalier that lives long enough will eventually develop it, making it the breed's leading cause of death.

Under that huge coat is a genuinely fragile three-to-seven-pound dog with a real risk of a collapsing windpipe, a slipping kneecap, and dental disease that starts young, not the low-maintenance lap ornament the coat photos suggest.