@turkay1-- I'm not sure about how long fresh vitamin C in juices last for, but fresh fruit juice is definitely much healthier than store-bought ones. I always make my orange and apple juices at home. The only one I don't make is grape juice which is really hard to deal with. That I do buy from the store.
I think the other thing to consider is how much sugar and carbohydrates are in the juices. Every fruit has different levels of sugars, so I think fruits with high vitamin C levels and lower sugars are the best option. Oranges and apples are pretty good. Another thing is that when you have fruit juice versus the actual fruit, you're not getting the fiber that's in the pulp. This can be an issue for people with diabetes because it raises blood sugar too quickly. So, a good option would be to include pulp in the fruit juices too.
I actually like grape juice more than orange juice though because you only need a cup of grape juice for your daily requirement for vitamin C, whereas you need about 8 cups of orange juice for the same.