Spain transportation

I also don’t know the schedules, but I believe the trip to be around 10-12 hours by rail, depending on the train selected. There’s probably a night train, but cost may be high. The buses I’ve taken for daytrips out of Madrid and back were as comfortable as the coaches we have here…sit up high, large windows, storage under the bus. What about a cheap flight? Air Europa or Spanair would have the best fares for non-stops…Tap or Iberia would probably be higher but will also have non-stop options. Flight is approx 1 hour.

I would probably take the train just because of the distance but haven't looked at the schedule either. The train system in Spain is not as developed as in other parts of Europe. The result is an excellent bus system with great buses and cheap fares. The luggage is stored below.

While the train service is excellent in Spain and Portugal, links between the two are atrocious. There's only one train/day between the two cities....it's an overnight train, and yes, it is expensive. That should improve if they ever get the high-speed rail link built between the two cities.
There are only two buses/day...one daytime and one overnight. The run is about 6 or 7 hours, depending which one you take, and costs about 40 Euro.
I've opted to fly that route instead. Vueling, Spanair, and Easyjet all fly that route....and you should be able to get a ticket, all in, for about 50 Euro.

...and yes, the buses are windowed with luggage storage below. They're actually quite comfortable, much more so than what we see here, and you may find headset plug-ins for music or the movie the driver may put on.

We took the train from Cadiz to Seville last fall and one lady had her suitcase taken from the luggage rack so be careful and dont let your bags out of your sight. Other than that the trains were fine and not expensive.