I've used both a bunch. Both are great scopes and there are things I like better about both.
Optically I think the Leica has a slight advantage over the Swarovski. I think the Swarovski is more durable than the Leica, but I like the fine focus on the Leica.
One thing I can tell you for sure is that an image is better when filmed through a Leica vs. a Swarovski, especially in low light.