Full-text catalogs are imported and ready to serve queries faster than with Rebuild. Note that Import does not use the new ...

Full-text catalogs are imported and ready to serve queries faster than with Rebuild. Note that Import does not use the new and enhanced word breakers that are introduced in SQL Server 2012, so you might want to rebuild your full-text catalogs eventually. If a full-text catalog is not available, the associated full-text indexes are rebuilt.