To help you choose which board is best for you, here is a run-down on what each board is good at.
The 3D board is the most popular and versatile board of the the two. It gives a birds eye view of objects such as furniture, products or buildings. Interiors of buildings can be generated, but the roof needs to be removed to see inside. This can be helful to see how several rooms may relate to each other. The 3D board is best for smaller objects, however it can be used for interiors and exteriors of buildings. See handy hint number 7 to get an idea of how it could be used. The 3D board complete pack comes with an ellipse template which is super helpful for drawing circles in 3D (perspective). The standard size 3D board is supported with an exercise book to help you draw all the things you may come across as you develop your design ideas. The 3D board is best for hobbyists, kitchen designers, cabinet-makers, furniture designers, students, woodworkers and builders.
The Archi-Board is restricted to drawing objects that are bigger than us, but it does this better than the 3D board can. If you draw an interior of a building with the Archi-Board it looks like you are inside a room. This view is more realistic than the bird's eye view the 3D board would provide. The Archi-Board is specialised for interiors and exteriors of buildings and is not suited to drawing smaller objects such as furniture or products. The ellipse template is not suited for use with the Archi-Board, and it does not have an exercise book for practice. The Archi-Board is best for interior designers, building designers and landscape designers.
To see the different kinds of drawings possible on the 3D board and Archi-board go to the gallery.