Photographers are a picky lot, and many have a favorite camera case they won't part with for love or money. They will endlessly argue about the advantages of a backpack style over a shoulder holster, whether you want a hand-held camera case or a rolling camera case and which kind of interior layout is best. One of the main points of contention, however, is whether a hardshell case or a soft side camera case is best.
Hardshell camera cases are made from injection-molded hard plastic, while soft camera cases are usually made from high denier nylon. You can also get leather camera cases, but these are quickly losing favor in response to the versatility, stain resistance, and strength of nylon.
Some photographers favor hardshell cases because they're virtually indestructible. If you're traveling around the globe and have to check your camera bag, you'll probably feel better using a hardshell case. If you're boating down the river and there's a danger of your camera case falling overboard, a good hard shell camera case will float, which can save you thousands of dollars. Who wants to see their camera and gear at the bottom of the river?
That being said, most hardshell camera cases are heavy, cumbersome, and can be difficult to pack. There's usually not much versatility built into the interior, so you'll have to stick with the default packing method the manufacturer has designed, even if it doesn't seem practical or intuitive to you. If you want to carry your gear around in a backpack-style case, a hard shell camera case won't win points for comfort. It will tend to dig in at the shoulders and isn't going to conform to the body at all.