I've learned and used many of the major players and some minor ones in the CAD market: AutoCAD (currently using at job), ProE, NX, Catia, SolidWorks (school), Alibre (internship), Sketchup, OpenSCAD (personal). Once you've picked up the ideas, it's mostly just learning the interface and use of a program. They all will do extrusion, you'll just have to learn the command for each one. I would say spend a good bit of time with 2-3 different programs. This will give you flexibility, just like knowing more than one programming languages is useful for programmers.
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I've learned and used many of the major players and some minor ones in the CAD market: AutoCAD (currently using at job), ProE, NX, Catia, SolidWorks (school), Alibre (internship), Sketchup, OpenSCAD (personal). Once you've picked up the ideas, it's mostly just learning the interface and use of a program. They all will do extrusion, you'll just have to learn the command for each one. I would say spend a good bit of time with 2-3 different programs. This will give you flexibility, just like knowing more than one programming languages is useful for programmers.