There is actually no easy answer to this question. Train travel in Spain is reliable but buses can be faster and more economical and it's always best to compare schedules and prices. Although the high speed AVE train from Madrid to Cordoba and Seville is the quickest option on this line. Spanish trains are predominantly operated by RENFE (http://www.renfe.es) but there are also regional train operates like Euskotren (http://www.euskotren.es) in the Basque Country For more details about train travel click here.