This is an incredibly popular question for any positions with a COPA component.
The interviewer will be looking for some of the following:-
AB can easily be reconciled with FI at account level through the use of cost elements. CB can only be reconciled at account group level (such as revenues, sales deductions etc) as values are stored in “value fields” as opposed to accounts.
In CB data is stored by posting periods and weeks. In AB storage is only by periods.
In CB transactions can be stored in operating concern currency and company code currency. In AB transactions are stored in controlling area currency, company code currency and transaction currency.
In CB you can create cross controlling area evaluations or cross controlling area plans. In AB you cannot as the chart of accounts may differ.
In CB the cost of good sales (COGS) are updated via material price valuations. Stock change values can be transferred to CB COPA during billing. Timing differences can occur if the goods issue and billing documents are in different posting periods. In AB the value posted in the stock change is posted simultaneously to COPA.