How do I become a 3D printer power user? (the which CAD question)

I want to learn a cad program, and am quickly overwhelmed by choices. Is there someone in the know who is willing to tell me the answer is 42?

If if helps narrow down, I've only ever used spice/altium/pcb layout tools before; my primary use case going forward will be enclosures and mechanical systems.

Thank you in advance; please do suggest how this post could be better! I'm aware that a recommendation question isn't exactly value-add.