It purely depends on what field you are in. ESRI is pretty much the preferred products for many, however in the engineering field Autodesk, is the best breed of products. Products such as AutoCAD Map, AutoCAD Civil 3D and mapguide. What makes these products unique is that both CAD and GIS is supported. In many cases your CAD/GIS poeple should be sharing data, very often this does not happen and you have two seperate environments that can share critical data.