There are only subtle differences between the visualization and animation applications Autodesk 3ds Max 2009 and Autodesk 3ds Max Design 2009.
You can perform the same operations with both of them. 3ds Max Design version has an additional module for lighting analysis (Exposure) useful for architects, and - unlike the Max version - it does not include the Software Development Kit (SDK) for 3rd party developers. Other functions, the file format and plugin compatibility are the same.
If you are a game developer, or use Max for film effects or special animations, pick 3ds Max. If you are a CAD designer, architect or mechanical engineer, choose 3ds Max Design.