The reason I ask what you will be using it for is to determine which set of features you need. If you're going to be using it for simpler activities, don't go all out for a Black edition with a 60fps, 1080p cam (all HERO3's are 1080p, anyways). The reason the Black Edition is so expensive is because of the crazy quality it has, and if you're using it for a more simple basis I wouldn't worry about the difference. The Silver or even White is perfectly fine for you. The main difference between these two is the white's camera has a 5 megapixels with 3fps burst while the silver is 11 megapixels with a 10 fps burst -- is that worth $100 to you?
Is GoPro still the best?
Versatility is a more subtle aspect to focus on when purchasing a camera, but it is vital to know what accessories you can use with your GoPro. The devices are known for their mix-and-match capabilities, and that means you need to be able to switch add-ons in and out when you see fit. There are many ways to enhance your underwater experience. Make sure your camera can handle them all.