Do you have a preference for material/color choice? What do you consider "stylish"?
How much protection do you want? Remember that more protection usually means more bulk. Do you want built-in screen protection? If not, do you want other screen protection?
Do you need open access to all ports at all times? Do you regularly use accessories (such as docks or headphones with strangely shaped plugs) that require completely unobstructed access to any given port?
Do you want extra features (a belt clip, a stand for video watching, a wrap for your headphone cord, or even an external battery pack)?
And finally, what price range do you have in mind?
The answers will help determine what would be the "best" case for you 🙂