choosing between Function Designer Diagrams and control Diagrams
What are the criterion for choosing one over other? Any limitations of Control Diagrams during Engineering or runtime compared to function designer.
What was the reason for ABB to introduce another POU?
Yes, agree with PurnaKiran. The CDE (Control Diagram Editor) has edge over coventional Control digram (CMD editor) and Function designer, where you have better look and feel and better engineering features. For more information, check the latest manual. However, may be this is interesting for you, BDM (Bulk Data Manager) is not supported by CDE.