Global handles are most effective when used to make general shape changes for a model, such as changing the basic shape of a model, stretching parts of a model, or making changes that involve the movement of many local handles.  There are three methods available for affecting the way global handles influence the model, the direct method, the hierarchical method and the mixed method.  The default is the direct method, where the global handles move the  nodes directly.  In the hierarchical method, the global handles move the local handles which in turn move the nodes, but if any nodes lie outside of local domains they will be unaffected.  In the mixed method, the hierarchical method is used for all nodes in local domains and the direct method is used for all other nodes. The hierarchical method maintains the shape of edge domains in the model, but if local handles are not evenly placed throughout the model, some parts will become distorted.  The direct method gives you what you expect but often distorts the shape of the edge domains.  For shell and solid models, better morphing is more likely to occur if you use the hierarchical method, and place local handles in areas where there is distortion.