A lot of people use retractable leashes! For years, they’ve been very popular. Speaking as a veterinarian, though, I wish they’d never been invented. Wanna know why?
First, they give your dog the wrong message. When he pulls against the leash, he is able to move further away from you. He learns that pulling on the leash is a good thing to do! Compare this to a no-pull harness or head collar; these discourage him from pulling and reward him for not pulling. He naturally stays near you.
Second, they make your dog unsafe. She can quickly dart 20-25 feet away from you (that little button is hard to use, to stop the leash from unspooling), so she could jump into the path of a car, or run up to a dog that will hurt her. If you’re in the middle of a deserted area, that much freedom is fine, but in our typical neighborhoods and parks, that much distance makes it difficult to keep your dog safe. Also, if she takes off when you’re looking the other way, the awkward handle can be jerked right out of your hand. Now, your dog is loose and is being “chased” by the plastic handle, which is gaining on her because it’s retracting…a lot of dogs in this situation panic and keep running!
Third, they make you unsafe. I hope you’ve never grabbed the cord when your dog is running; if you have, you may have sustained a burn or cut from the friction of the cord (there are actually people who’ve lost a finger that way!). If they wrap around your leg, they cause a lot more pain than a flat nylon leash would.
There is nothing safer than a sturdy 6-foot leash with the loop around your wrist and your hand gripping it firmly.