My Model-Creation App Criteria:
- Models to be used for manufacture via CNC mill, laser cutter, or extruder 3d printer.
- Primarily for mechanism type designs, with artistic/sculptural features to enhance aesthetics.
- Models to be shared with online communities, students, and family members.
- Low-cost in the short term and long term.
- Accessible to students, family.
CAD fits the bill for design needs. CAD models are solid, avoiding most 3d print errors. They are dimensionally driven (parametric); once you have a feel for how much clearance is needed between a "peg" and a "hole" on your 3d printed parts, that clearance can be used in all future designs. Most CAD apps include at least a modest tool set for aesthetic features.
A separate polygonal app with compatible import/export formats will allow for additional aesthetic flexibility. Also many of the 3d printer models available online are in stl format, which is polygonal and does not import well into CAD.
For fancy formulaic shapes, a scripting app would come in handy.
Open source apps are perfect for low cost and accessibility by all. Also consider that a model format which is not open source, it can be unexpectedly purchased, application prices can go up, or the format might be discontinued. If that happens, you may find yourself locked out of the apps and unable to work in the native format of your designs.
FreeCAD: hopefully this can fill the traditional CAD tool set
Blender: a polygonal app
OpenSCAD: scripted modeler