You'll notice the size difference immediately. The Rottweiler stands 56–69 cm (22–27 in) tall and weighs 36–60 kg (79–132 lbs), making it considerably larger than the Cavalier King Charles Spaniel at 30–33 cm (12–13 in) and 5–8 kg (11–18 lbs).

For families with children, the Cavalier King Charles Spaniel is the significantly stronger choice. With a kid-friendliness score of 5/5, the Cavalier King Charles Spaniel's affectionate nature makes it a natural family companion.

The Rottweiler needs slightly more exercise (4/5) than the Cavalier King Charles Spaniel (3/5), but neither breed is at an extreme. Both have high to moderate energy levels, so the difference in your daily routine will be modest — perhaps an extra 15-20 minutes of activity for the Rottweiler.

Life expectancy favors the Cavalier King Charles Spaniel: 9–14 years versus the Rottweiler's 8–10 years. For many families, those extra years together are a compelling reason to lean toward the Cavalier King Charles Spaniel.

Purchase prices are in the same ballpark: $1,200–$3,500 for a Cavalier King Charles Spaniel and $1,000–$3,000 for a Rottweiler. The initial investment won't differ dramatically between these two breeds.

One of the most important factors in choosing between these two breeds is temperament. The Cavalier King Charles Spaniel is typically affectionate, gentle and graceful, making them well suited for apartment living, families, seniors and first-time owners.

Both breeds score 4/5 for trainability — you'll have a similar experience training either one. Both are cooperative, eager learners.

Both breeds shed at the same rate (3/5), so fur management will be identical for either choice. Expect a moderate amount of loose fur from both.