Scizor's great bulk (70 / 100 / 80) and Defenseive Typing and Roost allows Scizor to set up multiple Swords Dance. It also heals Scizor, so you can keep it healthy.
And Scizor is a Bulky Sweeper.
Agility Scizor is only viable on Gen 3, because Roost and a lot of good attacks didn't exist in Gen 3. And it's role was baton passing, since it's only good attacks were Steel Wing and HP Bug/Rock.