going back a week or so. italy is way more historic, better arch than spain. spain is more new worldy. nice tho, not discouraging spain. better for drinking and meeting locals.
milan sucks. venice is otherworldly. crazy great city, but disneyfied. plan everything around crowd avoidance/off the beaten pathiness if you go there. bologna is a great stopover between rome and venice. great city off the tourist circuit. rome is probably the greatest city in the world.
if you go to spain, and go to more than just madrid/barcelona, try to hit portugal. well worth the effort.
paris is also great. hard to do well as cheap as italy/spain.
trains are great in italy, suck in spain. spain has buses. don't forget about the budget airlines, tho. may make more sense than training/chunnelling all over the place. don't try to move too much in 10 days. gets old. don't be afraid to rent a car and drive. just don't keep it/use it when you're in cities. but can make life super easy for getting between cities, seeing the countryside.