I'm the same size and use both depending on the shoe. For suede I usually use small to ensure they don't stretch. For shell I usually use medium. I don't think it really matters that much though because the small will still fill out the shoe and I doubt the medium would stretch a size 8. But I have both and decided to split them up that way. I'm sure other members on the board are more knowledgable on this topic, but I wanted to share my experience since we're the same size.