what design software do you use and why?
Discussion
I use them all
My preferred - OpenSCAD
FOSS parametric CAD program
(Problem - GUI is from '94)
Currently using - Fusion 360
Free* to use but a learning curve for some
(Problem - uses lots of computer resources for more complex models, limited free use, ~$600/yr. to use full version)
Starting out - TINKERCAD
Excellent kid-like program to use and make great models; works great for basically everything you need, web-based, free.
(Problem - web-based only, there are limitations but you can be creative to overcome them)
Many great projects made from tinkerCAD