A healthy size butt is just that: healthy.
Those with more glutofemoral fat are less likely to have the deep gut, so called visceral fat around their organs.
Visceral fat promotes inflammation in the body, glutofemoral fat is not as like to to do that.
Those with visceral fat have more insulin resistance and diabetes, than those who carry their fat in their butt and hips.
Gluteofemoral fat is associated with protective levels of blood fats such as cholesterol.
In general, those with gluteofemoral fat and not as large a waist circumference have better cardiorespiratory fitness.