Here are some older threads comparing the two.

http://www.bikeforums.net/showthread.php?t=50156
http://www.bikeforums.net/showthread.php?t=5341

I've had both bikes, love them both. But the 520 was mangled in car accident. I replaced it with a 26” wheel touring bike. The 2001 CD ti is still in the garage and i will ride it until the day i die.