Hi Wolfgang,
I'm not sure which specific items of the BOBI infrastructure would be improved compared with BI 4.0. However if you are using SAP HANA as a data source BI 4.1 would be the preferred option as it will allow you to use an SSO enabled OLAP connection. You can find more information how this works and how it can be setup is this blog: Design Studio 1.1 - Using an OLAP SSO connection on the BI 4.1 platform to SAP HANA.
Furthermore there is now an integration possibility between Analysis for OLAP and Design Studio: After you create a workspace in Analysis based on SAP BW or SAP HANA data, you can export it as a Design Studio analysis application for flexible use by mobile or desktop users.
With kind regards,
Martijn van Foeken | Intenzz