So the only cape that remains is possibly Dr Strange's, which can generate its own thrust and carry the superhero! :D
In the case of Superman, the cape is clearly decorative. But in the case of Batman, I don't know. Some movies portray the cape in ways that could conceivably make the fall lighter, depending on which material it was made of. I'm imagining myself opening an umbrella and holding it so that it's behind me, and then running as fast as I can. I think it's gonna slow me down. If Batman has some kind of fabric that is light, some kind of skeleton that mimics the bat's bones that hold its wings open, I don't see why it couldn't potentially be of service.
As I mentioned, having the cape floating & freely designed, it doesn't really make a difference as reduction of terminal velocity is concerned... So, if he could have the skeleton, it could do some parachute's work....
Thanks for your insightful comments, you're appreciated!