Choosing the best iPhone case depends on your individual needs. There are basically four types of iPhone cases: plastic, leather, rubber and metal. Now, let’s review each case type.
If you are looking for maximum protection against accidental drops and bumps, a rubber case (silicone iPhone case) will perform better than the others, they will provide a good grip as well. Note that rubber cases are tend to hold more dirt on the surface by time. If you buy a rubber case, you should clean it time to time.
If your first priority is the style and quality, I would suggest a leather case. They are mostly durable than the others. The only disadvantage we can state that they are more expensive than the other iPhone cases. Some models add bulk, some not. Just beware of imitation leather cases for iPhone and be sure that you are buying a genuine leather case.
Plastic cases can look very pretty in many different colors and can be manufactured real thin, but beware that they provide little protection against falls and hits. They are generally the cheapest cases. Some people like to change cases regularly and buy few of them together.
Finally, there are very protective metal cases for iPhone. They are designed for people who have a very active life and can easily abuse the device. You will feel like your iPhone is in a tank. Note that they usually add bulk to the device. Actually, as a style I like them as well.
Overall, the best decision is to make a short list of your individual needs and compare the case models according to several factors: Price, Material type, Texture, Style, Color, Durability, Bulkiness.