For some time now, the older version of the Ancestry.com website has synchronized both details and sources with the FamilySearch.org Family Tree. Unfortunately, for some time, the newer version of the website was lacking that feature. Now, the ability to synchronize data between the two programs has been added to the new, updated version of the Ancestry.com website. Here is a screenshot showing the link.
The link allows you to do the following:
When you compare a person on your Ancestry.com family tree with the FamilySearch.org Family Tree, you get a screen that compares both details and sources between the two programs. You can then move the information, by clicking the check boxes, from one program to the other.
You need to carefully consider which of the information is correct and make sure that the sources really apply to your ancestor or relative. The process is completed when you save the changes.
This is a big benefit to those who are keeping most of their information either on the FamilySearch.org Family Tree or on Ancestry.com.