i have both. i got the duomo for christmas 05 and the speedy the day it came out. both are lovely bags and i use both, and would never get rid of either unless i had to.
they make look alike in picture, but in usage and function they are totally different. i will attach pictures so you can see the difference. the speedy is like a bottomless pit...it holds so much. the duomo on the other hand is very structured and cannot hold nearly as much as what i carry in my speedy on a daily basis.