When ever you need to migrate to from one vCenter instance to another there are lots of things you need to migrate.
This PowerCLI script will help you migrate members from one DRS VM group to another. It can easily be modified to be part of a bigger context, or migrate all groups available.
Prerequisites
The prerequisites are that you have both the new and the old vCenter running, and that you have disconnected you hosts in the old vCenter and connected them to the new one. Do NOT remove them from you old vCenter. Leave them disconnected.
Continue reading PowerCLI: Migrate DRS VM Group Members