Alignments for Faceted CAD models such as .stl

[[Je...]]

Hello.  Does anyone have experience working with faceted CAD models such as .stl files?  More specifically, I am working with a model that does not have a lot of prismatic, standard geometry, and the model does not drop in "square" to the trihedron.  Do you typically use RPS freeform or 3D best fit alignments for this type of situation?  Any other suggestions?

My main task is to compare the actual part to the CAD, and I may simply use CAD face points or curves.