I remember that - at least in the initial phase of discovery - the multiwall variety was actually easier to make than a single or double walled nanotube. An article I read showed an SEM photo of 7 nested nanotubes, for example. These would actually be preferable (I believe) for construction since not only do you have the tensile properties, you also have stiffness (from the nested tubes). From a chemical and electronic viewpoint, the single walled variety is more interesting since you can fill them up with metal atoms, forming nanowires.
Developing the ability to control the reaction to get the products you want is the key.
Better living (and researching) through chemistry.