rats are a lot bigger (size of kittens sometimes) with broader bodies and longer noses they will also scare the Cr*p out of you. Mice on the other hand are quite sweet in a vermin type way, and will make you feel guilty after you kill them, I blame that "american tale", when a small mouse loses his mum and dad and is lost in america and ... 'there are no cats in america and the streets are paved with cheese'... ahhhh get me everytime
having had pet rats I can say that a rats tail is not hairless. i just looks that way because there are not many hairs there. Apart from the size of the creature the tail is usually the bigest give away a rats tail is usually as long as its body whereas a mouses is usually shorter than its body.