Thanks.
New mode allows the hull of the mesh to be defined quickly. Alternatively, the Create tool can be used to create vertices and edges...
Those two sentences are a bit ambiguous, but I think I figured it out. Please correct me if I'm wrong:
1) Initially both "New" and "Create" can create a new deformation cage. Using "Create" may take longer as it requires some edge clean-up
2) however, if you want to modify the cage (not to be confused with "Modify" tool) by adding more pts or edges, then you can only use "Create".
3) ultimately cages created from either tool have the same effect on the bitmap image.
Would that be fairly correct?