Solidworks is the absolute #1, but very expensive (about $4k, unless you want to play the crack game).
Fusion 360 is #2, unfortunately I can't use it anymore
Freecad has a good reputation but I don't see it being far superior to Design Spark Mechanical, which I use satisfactorily.
Sketchup, although being widely used, does not offer the accuracy needed for small parts IMO
You must be aware of this difference: Solidworks and Fusion 360 are both true parametric, which is a great value if you need to produce variations or iterations of a product, DSM is not parametric, neither Freecad AFAICS.
Basically, at my humble level, it means when I flunk, I have to restart from scratch.