Below is a link to a paper (2007) on 'Technical Notes from experiences and studies in using Parametric and BIM architectural software."
They make some bold conclusions including, "With our experience of modeling in both CATIA V4 and Digital Project/CATIA V5 we find it takes approximately three to six times longer for production modeling tasks and iterations in Digital Project/CATIA V5."
What?? You guys aren't finding a 3-6x time increase are you?!
I don't know how they would make a fair comparison but i can't see GT going something that wastes time.