APO DP and SNP compare to ECC Demand management and MRP

Hi Experts

We have a APO project for our client. 

Basally, DP will run baseline forecast consumption forecast based on historical data ( moving average),  maintain the consumption forecast in Demand Plan, Then Release to SNP  to run heuristic for the procurement , and check the stock position.

Our client have a question, say why APO, why not MD61+MD04 (MRP)

To me, DP have a consolidate view, statistical forecast, easy maintain forecast, with the attributes.  SNP is a ready time, consolidate book compare to MD04. I do like the stock projection in SNP during the simulation.

The feeling like, you have a car, but you don’t want use the car, instead you want carry the car and walk.  But I don’t have a killing point that we must use APO. 

However does SAP have a comparison the DP+SNP to ECC Demand management and MRP?   , I want a summary of the comparison and maybe a killing point that we must use APO.

Thanks a lot

James.