You can "prove" this by looking at the glycemic index. Glycemic index is not a napkin math thing, its done by making people eat or drink something and watching what their blood sugar does.
A raw orange is 31-40.
Orange juice is 46-54.
Coca-cola is 63.
I think juice may be a _LITTLE_ better than soda. I still choose to drink neither, and think I am better off for it.