AVE vs. Altaria rail lines?

Both are high speed trains. The AVE are replacing the Altaria. I don't think there is much difference. Surprised that you have a choice. I would go with the schedule. And second class on those trains are excellent. Personally don't think first class is worth the cost.

Thank you for your reply - that really helps. The choice only comes up in the time slot we prefer so there you go! Many thanks again.

On my trip to Spain in February 2011, when I took the AVE (Madrid to Seville), the train was the newest and fastest (and most expensive). When I took the Altaria (Granada to Madrid), the actual train was older (heavy metal tray tables, bonked myself hard in the nose with one!), and it started out on "regular" tracks, then it joined back up with the high-speed/AVE tracks at Antequera, and it appeared to be travelling at the same speed as an AVE train after that. So I assumed that Altaria was AVE/high-speed most of the way, but not all of the way, so it had a different name and was slightly cheaper. I know the AVE trip from Madrid to Seville takes 2.5 hours. Looks like the "slower" train from Madrid to Seville takes 2.75 hours and is 20 euros cheaper in 2nd class (and 1st class). I chose the AVE because it comes hourly, and I wanted more time in Seville on my day of arrival; I missed the early cheaper train (10 am), and I didn't want to wait around until 4 pm for the late cheaper train. If it were me, if they came at the same time, I wouldn't shell out the extra money for the AVE or 1st class if I had the choice.

The difference is that in Spain high-speed lines are standard gauge while traditional lines are broad gauge. The AVE trains can run only on standard gauge while Altaria have telescopic axles so they can leave the high-speed lines and continue further over traditional lines. For Madrid-Seville the journey times should be similar.