I started out making Hauser copies, but always found the shoulders and base to bit a bit flat. I switched to the Santos Hernandez plantilla for a while, but in the end came up with my own shape which was somewhere between the two. For me, the important point is that the radius of the curves should change gradually around the outline, rather than be composed of a number of different radii joined together. To me these are less pleasing to the eye. I think you can also tell a good plantilla by how easy it is to bend the ribs accurately to it.
James Lister, luthier, Sheffield UK