If you use at&t's test, you are testing from you to the edge of the at&t network, which would be the only part that at&t can fix if you did have a speed issue. You can use other test sites, but you are adding portions of the internet outside of the at&t network that can affect your speed and can not be fixed by at&t if you have issues. If I am concerned about speed from at&t then I would use their test. -- GUN CONTROL: using both hands
