The best comparison to these solid modelling programs is a car. Whether you have an Audi, a Chevy, a Hyundai, or a BMW, the very basic function is still the same. The buttons may be in slightly different locations. One may accelerate a bit faster. One may be a bit more comfortable. But, it seems at this point, you're still just getting started, and, like a new student driver, no matter which car you take, you're gonna be going ten miles an hour below the speed limit and stopping the full 3-mississippis at the stop signs. To build off of Meaker's response, pick two or three, and research which of those have the best online help, or youtube tutorials, because that's what you'll be learning from in most cases.
Personally, I use Autodesk Inventor, and have been using it for almost 5 years now. The student version is free with a .edu email account if I recall correctly, and it's not a bad program. Just like the cars, once you learn to drive one, the others are 90% the same. If you do choose to go the Autodesk route, the help that I have needed from the Autodesk website has been fairly helpful.
While a bit dated, this is the book I used. It's pretty damn good and teaches you through step by step examples, not overly technical symbollic formulas and the like. This is just what I used, and I didn't search around for it, but figured I would throw it out there in case you choose to pursue. https://books.google...id=P5auoAEACAAJ