Context is very important here. Neither one of these will CAUSE weight gain or weight loss. But depending on your goals, they can help.
Weight loss is a popular topic here, but there are people out there who struggle to gain weight. When it comes to gaining weight, one of the first things I like to recommend is drinks like the above. When you want to gain weight, the goal is to maximize your calories and minimize the volume of your food (so you are less full), and juice is a great way to get calories & micronutrients in without filling up.
On the flip side, if you do want to lose weight, the first thing I would do is avoid drinks like this. For weight loss, we want to minimize our calories but maximize our volume (to help us feel full) so eating the same amount of calories as food vs drinking them will help us.
Just think about it. Which one will make you feel more full: drinking 15oz of liquid, or eating one and a half apples, an orange, half a mango, and 2 and a third carrots?
“But what about all that sugar?” Yes, fruit contains sugar. But it’s not going to stall your weight loss efforts. The MOST IMPORTANT aspect of weight loss is total calories. If you are in a caloric deficit overall, the sugar you are eating in fruit will not negatively affect you.
Also… it’s fruit. Nobody is gaining weight from eating some fruit.
Remember, these things are not mutually exclusive. You can drink fruit juice and still lose weight. You can also eat fruit and still gain weight.
There’s nothing wrong with choosing to drink your calories or choosing to eat them instead. But depending on your goals, it can make a difference!