People's digestive system is not actually set up to process milk very well. Although you get a good dose of calcium and vitamin D from milk, you can get these things from other sources, without running your system down. Milk and milk products can enhance allergies and intolerances to food and other outside stimuli, and increase mucus production. I don't know if orange juice is 'better' per se, because the vitamins it provides are completely different. I can say your body processes it easier, it gives you a bunch of vitamins, if the juice doesn't have sugary additives it isn't as fattening, and it doesn't have all the nasty side effects that milk can have, (whether you notice them or not... in fact you probably wouldn't notice them unless you cut milk out of your diet and then tried putting it back in). So I guess my vote is Orange Juice.
Which is better for your body: orange or milk?