There is a considerable improvement in the render times from RDS 5 to 5.5 and then a modest gain from 5.5 to CAR. If most on your work is built out of primarily geometric shapes as your example then the free form modeler should work fine. It seems you are already familiar with that. The disadvantage is if you need to convert them to obj or some other format for export, not easy to control unless you want to spend a lot of time at it. I'm not familiar with other 3d apps.