If you tune modern Euro diesels (EDC17C64, EDC17CP44), the 2.70 update is essential. If you only do old Benzes and VAG 1.9TDIs, stay on 2.25.
Once v2.70 is installed:
The primary advantage of moving to 2.70 is the inclusion of new protocols, allowing you to interface with a wider range of vehicle makes and models that were previously inaccessible on 2.25. Update Ktag Clone From 2.25 To 2.70