When there is draft analysis if two options are exist on selecting the plane (one is origin plane and other one is planer face on the part) which one is most preferable?
Depends on how the part is built. If you do a draft analysis using a planar face and notice all the draft angles skew in one direction, the planar face might be tilted, and you should use the reference plane. If you do a draft analysis relative to a plane and draft looks symmetrical, then you're ok using the plane.
Some parts are created at random angles, and you have to find the direction of pull if it's not already identified. It might be best to use the Move Body tool to orient the part relative to the base coordinate system. You might even go one step further so everything is clean and round trip export/import to get rid of the Move Body feature.
Retrieving data ...