OpenSCAD is great, but a bit limited. Also latest release is almost 4 years old, could do with some further development.
FreeCAD is very capable, but it is a bit buggy and not very user friendly.
Solvespace looks really neat, but also a bit limited and from the looks of it isn't actively being developed. Those two points make me hesitate to invest too much time in it but someday I think I will play around with it some more.
Blender isn't CAD software, but it is the gold standard in my opinion. Sacrificing nothing and a really good UI. But it is more free-form than architecture and technical modelling. So wouldn't recommend it if that doesn't align with your purpose (look up blenderguru donut tutorial for an excellent start).
All the mentioned applications are pretty odd in how they behave though. It requires that you commit to learning it.
Personally I've used OpenSCAD quite a bit and I've now committed to learn FreeCAD. I had trouble creating maintainable code for OpenSCAD for anything but small projects, and also it takes some effort to create visually pleasing parts with it.
It is hard to find good material on all the software above (except for blender), I really liked this (hard to find) 3-part tutorial for FreeCAD. I have had huge help from it and it is what helped me to grok enough of FreeCAD to start actually attempting to do anything on my own. If you are curious about FreeCAD maybe it will give you a better idea of it than only playing around with it yourself.
Part 1: https://www.youtube.com/watch?v=6dJEPg06G-o
There's a "2019.01-RC1" tag on github, so we can probably expect a new release soon.
For programmers, one can also use Python to define more complex parts or workflows.