Which would be the most similar to animals in the same class or two animals in the same phylum?

Animals in the same class share more specific similarities than those in the same phylum, as class is a more refined classification that groups organisms with closer evolutionary relationships. For example, within the phylum Chordata, mammals (a class) have more in common with each other, such as characteristics like warm-bloodedness and mammary glands, than they would with reptiles or birds, which are also in Chordata but belong to different classes. Thus, comparing two animals in the same class is typically more relevant for understanding their similarities than comparing two animals in the same phylum.