I use the exact same leash you just bought & love it. We started out using the tiny one but I eventually upgraded in size b/c (same reason) hubby couldn't fit his hand in lol. Raja couldn't be happier with the extra length - it's only a 6ft. difference but he doesn't pull nearly as much.
I never use the old one anymore because it's all that thin cord, as opposed to having the actual bit of leash on the end. If Raja gets tangled on it the leash won't hurt him, but I fear the cord wrapping around his legs could hurt or burn. Great choice! I recommend Bags-on-Board to use with it.