I feel hanging is more efficient over the long term, especially than manual stretching. You have no idea how hard you are pulling, nor for how long. With hanging, you always know the exact resistance (weight) and exact time.....sets are 15-20 minutes watched on a clock.
In reality hanging is limitless as you have many more options over time with adding more weight in small increments as your penis adapts. You can only pull so hard with your hands and again, you never know how hard "hard" is with manuals.
Try coaching a guy on a manual routine. :D. "Ok now pull "hard" for 30 seconds....." Too much guessing with manuals and in reality more fear because you don't know how hard you're pulling, so you likely hold back fearing injury.