Generally speaking there really aren't "bad seats" that cause you to "miss the show" - however more towards the edges, you do have a more "extreme" angle to watch the show at, thus it is a different perspective. This is why they have "Category 4" that can only be sold at Cirque itself, and why Cat 3 is pretty cheap compared to the other seats.
Generally speaking though - The different sections do have their advantages and disadvantages. It's much like sitting in a movie theatre. Where would you sit? If you like to sit up front, you'll see a lot more intricate details, such as make-up and facial expressions, but you will be "looking up" during a lot of the show. If you sit farther back, you will have a better over-all view, however you may not see the same make-up and facial expressions as well. So it is totally up to your preferance.
You can watch the show many times, and still see new things.