18 days - Spain or Italy, or a little of both?

Since you're already flying to Spain, my vote would be Spain. I think you could have a really nice trip with 18 days, seeing quite a bit without being too rushed (and then feeling like you need to come back soon). Obviously they are both worthwhile countries and you should visit both at some point, so do Italy next time, and fly right there.

I agree with Christy. Spain's a fascinating place, with lots to keep you busy for 18 days (don't forget Granada!) When you come back home, start planning for Italy!

my vote is with Christy and Norm. If you go to Italy, you'll want to see so much that you'll spend too many of your days traveling (madrid- rome, rome- florence, venice, cinque terra, etc,) and still have to make it back to spain to leave. This is not even talking about the places in Spain you'll want to visit- the next thing you know, you'll be wondering what happened to all that time you had, and realise you spent it all in train stations and airports! Ay carumba!
Yep, my vote is Spain this time, Italy next time.

Thanks everyone, we're about 95% convinced to stay in Spain. In full disclosure, we got an incredibly good price on the ticket to Spain, and I had found $10 airfare from Madrid to Rome, which is what sparked our thought of doing Italy (instead of Spain)
in the first place. But from your thoughts, it sounds like I'd be spending too much time travelling to accomplish both. Although the decision is tough, it is an enjoyable one!