Every university theatre program is different, and every professional theatre is different. For the most part, academic theatre and professional theatre are worlds apart.
But if you go from your theatre club to a community theatre (non-union), you might find that things aren't all that different. People are still costuming the show from their closets and the local halloween store, you might still work 12-hour shifts, and there might still be a lot of MacGyver theatrecraft going on ("if we bolt some PVC pipes together as a frame and used a trash bag, George could pull a string and the snow would drop..."). The doing-it-for-the-love attitude most students adopt goes a long way in community theatre where without funding or professional resources, love is often the only thing that brings a successful show to the stage. On the other hand, you might find that your theatre department had a lot of luxuries - a prop storage, costume stock, rehearsal space availability - that you won't find as easily (or cheaply) in the real world.
Unions change everything. Not better or worse, just different. It depends on your style of SMing and your personal goals, etc, whether union regulations feel liberating and validating or stifling and frustrating. I felt, as KC did, a new level of respect and awareness from the other company members when I entered the professional arena of SMing. I felt like people finally understood that I was here to do a lot more than bug them about call times. However, working with unions means that you can't do some of the things you did in academia. For example, in an IA house you can't run onstage and move props/furniture. The first time most SMs coming from an non-union world encounter this, it throws them for a loop; It feels like you can't have the get-it-done attitude you had before. If you were a workaholic-style SM where your theatre valued you because you would prop the show, check the dimmers, and mend the costumes in addition to calling the show each night, you might feel like half your job was just taken away. But really your emphasis is just more concentrated. Now you can pour all your energy into SMing and do that job better than ever.
This could turn into a pretty long paper for you, because there are so many differences, and yet no two theatres or academic programs are the same. Everyone's personal experience will be different - including your own. You might want to see if you can meet some local professioanl PSMs on site and talk about their typical duties. There are so many subtleties you might never have thought about. Even after writing an A+ paper, the real answers to your questions will only come once you yourself have transitioned from academia to the professional world. Best of luck (on your paper and all the rest)!!