Cats, because the range of their weights is less than that of small dogs.
This can be determined by visually observing the distribution of dots on the dot plot for cats and small dogs. The dot plot for cats shows a more concentrated distribution of weights, with most of the dots clustered around a narrower range of values. In contrast, the dot plot for small dogs shows a wider spread of weights, with dots appearing across a larger range of values. This indicates that there is less variability in the weights of cats compared to small dogs.