Have you ever seen a greyhound go full speed? Your GSD wouldn't stand a chance. Remember, top speed is only for a little while. So a dog can go much faster, much longer than a cat, but they probably do have around the same top speed. Each breed has their own characteristics, a GSD is faster than a husky on short distances, but naturally a husky is better over long distances.
Cats are very fast over short distances, and therefor the top speed is quite high, I wonder what a sustained speed would be over a mile though.