What would a 9 year old better a guinea pig or a ferret?

Both are okay. Guinea pigs don't really smell that nice, but they aren't nocturnal. If the child wants to play with their pet often, a guinea pig would be the best. Hamsters are cuter and more affectionate. They don't smell, but they're nocturnal. They sleep in the daytime and will get stressed and irritated if the child bothers them in the middle of a nap.