IMS/DC is a dedicated front end for IMS/DB database. If you back end is IMS database, I will strongly recommend you to use IMS/DC as it fetches the data much faster than other online transactions. However, it cannot be used for other back ends.
CICS can be used for any back ends namely IDMS, IMS, DB2. If you are using DB2 as back end, i will recommend to used CICS as front end.