There are several aspects to keep in mind.
Do you have to check your luggage?? We get to take our luggage onto the aircraft so I don't need to worry about the luggage handlers dropping it. Of course, that means you are limited as to size. What will fit in the overhead or closet?
Are you tall?? I'm about 5"9' (177cm). Many of the cheaper suitcases have handles that are just too short for me and I would have to walk bent or I would keep running into my own heel.
How long are your trips/ or how big are your shopping spees?
Soft cases can be a little bit more forgiving if you need to cram stuff. Of course, a strong zipper is a must on that. There are options of expanding suitcases.
Well, I started out (18yrs ago) with the company issued pull (on a leash!!!) suitcase. Boy, it was a pain, because you had no place to put your flight bag and the thing would tend to fall over. I replaced it with a hard cover upright samsonite which we checked back then and it held up pretty well. When the handle finally broke I bought a Briggs & Riley upright (soft). It has a second zipper which will add an extra 2 1/2 inches in depth if needed (so convenient for my shopping sprees!!!). It has a tall handle which is great for me. Briggs & Riley has a lifetime warranty on their products which I needed to use once for the handle. They sent it right to my house!! I bought a second one while the first was being repaired (I travel with kids, so I could use a second one anyway). I really like their products. I also own one of their tote bags that I use as my flight bag and a rolling tote that I use for what we call "turn arounds" (one day trips).
I hope this helps. I would suggest going in and trying them all out. Walk around the store, take tight turns, walk fast, as your stride becomes longer you'll see if the handle is long enough for you.
Good luck and welcome to the world of aviation!