They are both basically "CAD/CAM for programmers" - and allow for parametric models to be designed. In fact, there are more than a few models like that on Thingiverse, so if you needed to resize something to fit your needs, you can (plus tons of gear and other similar custom power-transmission systems).
Of course, that's all for design and modeling - it wouldn't help for other problems, where some form of calculation and checking of a "model" (in the sense of a simulation or idea - not necessarily a complete physical object rendering) is needed.
You see a ton of these kinds of tools in the electronics and hobbyist realms; quick calculators to tell you how much resistance to use for various LED configurations, or 555 timer customizers for common circuits - things like that. I know of one out there which gives you torque/power curves for a variety of different RC hobby electric motors. There are of course several for physics simulation and testing, too...