As usual there are a few questions that need to be answered before you make your decision. The first thing you should do is figure out how you will use your handheld. That is, in the case or out of the case. Some cases let you leave the unit in while you're using it, while others require you to remove the unit from the case before you use it. Next you should decide whether or not you'll need to carry anything else in the case with your handheld device.
Some cases fit snugly around the handheld leaving little or no room for carrying other things.
Other cases come with a multitude of zippers, pockets, flaps and other places to store things like batteries, cables, pens, etc. These cases are great for the traveler but not necessarily the best for people who just want basic protection. There are other considerations as well. Well you'll need to decide how much padding you'll require of your case. Once these questions are answered you'll be in a better position to start shopping.