Tool Creation - SolidWorks vs RobotStudio Center of Mass and Moments of Inertia Calculations

Hello, 

Has anyone here used SolidWorks to calculate the Center of Mass and Moments of Inertia calculations for a tool? 

I've noticed some variation between the values calculated in SolidWorks and those shown in RobotStudio when creating a tool and I'd like to get some clarification. 

In SolidWorks I see several options for inertia outputs:

1. Principal axes of Inertia and principal moments of Inertia: Taken at the center 
2. Moments of Inertia: Taken at the center of mass and aligned with the output coordinate System
3. Moments of Inertia: Taken at the output coordinate system.

When creating tools in RobotStudio, I've been using the 'snap gravity' + part selection and would use a merged part to snap the gravity, but I still see noticeable differences in values between the two methods and seems that they never align.

Is this normal? And in general, is it more accurate or recommended to use the data directly from SolidWorks, or to rely on RobotStudio's own calculations? 
 
Lastly, I've already created all my tools in RobotStudio-- is there a way to simply edit 'edit' an existing tool to manually enter the Moments of Inertia values, or would I need to completely recreate each tool? 

Thank you in advance for any insights or help on this issue.