EPMcopyrange vs LocalMember for calculations

Hi Gurus,

I have an input form where I need to calculate data for certain months and save it to the input data source. I am wondering whether I should use EPM copyrange or a localmember to do the calculation.

Example:

                    Col1-       Col2       - Col3   

                    TotalDS-TotalDS- Input

                    Actual- Estimated- Estimated

                    Jan15- Calculation15-Jan16

Account1 100        =100*1.1            110

Account2  200       =200*1.1            220

Account3  300       =300*1.1            330

Should I use a local member for column2 or can I just use epmcopyrange? The reason I am asking is because if I have to calculate in for 24 months, there would be a minimum of 24 local members. I need local members for other calculations as well. So we are talking about 35 local members.

Regards,

David