You'll drop pounds faster with water, but you will also be tired, weak, fatigued, headaches, dizzy, and possibly more. The Water Fast gets things moving out faster in the body. Don't do a Water Fast more than 9 days without supervision.
You'll still drop pounds with the juice, and you will still have some detox symptoms, but not as severe.
More importantly than fasting and losing the weight, is getting toxins out of the body and getting healthier. Along with what you will eat after the fast. You if go back to eating the way you were before the fast, you're likely to gain back all the weight, I know, I did it.