InCAD is just an add-on to SolidWorks to make transition from SWX to Algor easier, rather than having to export out the SWX model and import into Algor. I believe that it also keeps a relationship with the original model so that if the original SWX model changes, the Algor model will automatically see that change; meshing and boundary conditions may have to be updated. All analysis is still done in Algor.
I'm not too familiar with the SolidWorks extender.
--Scott
For some pleasure reading, try FAQ731-376