Zero.
Uh...rats aren't bigger than guinea pigs. Even large rats sold in pet stores are still smaller than guinea pigs (about the same length minus the tail, but still a smaller body). Also, guinea pigs are intelligent too, it's just that no one makes any effort to see that they are.
I love the sound guinea pigs make. It's so cute. lol.
But I love pretty much all animals, so yeah.