I would probably aim for Inventor or Solidworks. I’ve used both, and it’s not terribly difficult to go from one to the other. That and both are fairly common at the university level.
There are arguments to be made for other CAD programs, too. I’ve heard of one called IronCAD which is supposedly easier to use but just as powerful as Inventor and Solidworks, but I’ve never had a chance to play with it myself, just talked to someone who has used it–given the descriptions I might say that it’s close enough to be worth a look.
Given the overall target, I would prioritize “shallow learning curve” without sacrificing ability/power/portability.