There are other factors that can cause different results, such as mesh size, but assuming you set up the models similarly, the difference is most likely the geometry, as Rahul said.
There is a lot of variance even within each method you listed. The shrinkwrap tool in SpaceClaim can produce a good or very bad representation of the geometry based on the parameters you used. The mesh size specified in the shrinkwrap is a major influence, but there are other parameters. You should be able to easily judge whether the shrinkwrap was decent by visual inspection. If you use the autoskin tool, this is a good tool, but requires simple geometry. You may need to use the manual “skin surface” for what the autoskin cannot do well.