MSUP Transient Structural is a linear analysis, which means it includes a small displacement assumption.  If the displacements are large, that is one reason to run a full transient. 

Linear models can't have nonlinear material behavior, so if the stress exceeded the yield strength and you want to include plasticity in the material model, that is another reason to run full transient.

Linear models can't have nonlinear contact (frictionless, frictional, rough), so if faces are penetrating in the linear model, you can add nonlinear contact to prevent that from happening in the full transient.