pear juice provides you with more of vitamin C. Also, the major advantage is that pear juice will detoxify and cleanse the system while not inducing diarrhea, which is symptom of prune juice
Although both good sources of fiber, pear juice is gentler to the digestive system. In addition pear juice is also cooling for fevers or heat exhaustion, and can also relieve cold and sore throat symptoms.
When you have a constipated child they work at about the same rate of time. I suggest pear for children because they tend to like the flavor more and it makes it easier to get them to drink it.
If the reason you're asking about these juices is for laxative use, then I'd say pear juice isn't as effective, but in my opinion, tastes alot better than prune juice.
