I have a plastic part in SW 2014 Professional.  Using "Mass Properties", the volume is reported as 76.93cm^3.

We have a seat of SolidWorks Plastics.  I've run my part through analysis, and when the process is complete, the volume is reported as 77.87cm^3.

Why is there a discrepancy between the two?  Is the latter the effective volume of the mesh, and not the original SW definition of part geometry?  Regardless, why are they different?

(77.87-76.93)/76.93*100 = 1.22% greater volume in SW Plastics.  This doesn't seem insignificant.

Bottom line, which should I use for cost estimating material usage?  I've always trusted SW to get this right.  SW Plastics has disturbed my trust (for now).

Thanks!