FuzziOn is correct with his comments - I will just add that the old circuit was 2.61 miles, but the current version of the track is 2.47 (from memory). The changes were made to increase run off.
A lot of old layouts of tracks were better. Then they started slowing the drivers down with chicanes, widening corners so more cars would fit without bumping or crashing...luckily we can't die in GT6 so bring on the old layouts I say