Blender and 3DS (only old versions) are the only two programs for which a g3d export script exists. In theory, you can use other programs to create models and then import them into Blender. That's actually how I started out, using AutoCAD models, but I strongly recommend against it. The vast majority of the knowledge on this board is about Blender, not Maya, AutoCAD, or Wings3D, and Blender is free, extremely versatile, and it's what almost everyone here uses. If you were to use a different program, it makes sharing files a lot more difficult. In summary, stick with Blender if you can.
