For Transactional Commercial of the Shelf (COTS) Product the recommended path is to (re)use as much as Possible of the Out-of-the-box Logic in order to minimize the Customization Effort.
For Analytical Systems this is also possible, however creating new Objects and Leaving the Standard Completely separate has Advantages during Upgrades since only the new created Objects for the previous release might just be copied and pasted to the new Release.
Hence, there are two aspects associated with this Question:
Does the Customer want to:
- Optimize the First Implementation effort by re using the Analytics Object, too.
- Optimize the ongoing Effort by separating the OOTB Logic and the Customized Logic.
This Question should always be asked at the beginning of a new Greenfield Project since it will steer the Implementation in either direction.