ytrewq, thats one of the best answers I have seen on here for a long time. Honest, and from someone who actually knows the breed from personal experience.
I would add that even 'lazy' breeds need exercising, and I would dispute that the Leonberger is in that category, I know people who do Working Trials and Agility with theirs.
What about a Mastiff, they slobber and are a very big breed, but at the above poster said, all giant breeds cost more at the vets, more to feed, more to pick up(!|) and live less. As well as being expensive to start with.
Ask Gravitate, Boxers can do their share of slobbering too!