Use New RefWorks if:
To create an account in Old/Legacy RefWorks:
Use Legacy RefWorks for a project if it:
To migrate citation records from Legacy RefWorks to New RefWorks:
As a new version of RefWorks was being created, a series of corporate buyouts within a few years created a confusing environment for development and planning. Ex Libris seems to be adding some stability by committing to maintaining the old version of RefWorks (Legacy RefWorks) as long as people are using it, and accelerating development and fixes for New RefWorks*. For more details, scroll to the bottom of the Get Started page on this RefWorks Guide.
*Ex Libris/ProQuest announced on 1-31-18 that they will be maintaining Legacy RefWorks indefinitely.