I've owned both mice and rats - and after my first rat, I would never choose mice again. I love looking at them as they are so small and sweet, but a rat is more like having a tiny dog as far as intelligence and responsiveness goes. Plus yes - rats smell less. They don't have to smell at all, if you have two females (rats are social and need rat company) as I did, and clean the cage frequently enough. Boys are whiffier (we have three at the moment) but generally more calm to handle, especially if you get them as babies.
Daughter has trained the rats not to poop when being held, and is working on litter-training them in the cage so thy poop in one corner, making cage cleaning much simpler. Females take to this training better than boys. But boys get huge and squishy, like beany toys, and have cuter bellies. :)