Jessica....I'm not sure you can compare it that way....I've been on German trains where it's been very crowded, and Italian trains where we were almost the only people in the car. In any event, the trains you will take will be the AVE high speed trains....fast, modern, but expensive. For example, one-way fares between Barcelona and Madrid can be as high as 110-130 Euro for second-class walkup tickets. The trains to Toledo can be busy with tourists, while those to Sevilla and Cordoba will be busy on weekends (and expensive!) If you know your schedule in advance, I would urge you to visit the Spanish national railway site, RENFE, to buy in advance. Simply select "Buy Tickets" at the top center of the page, and go from there. Look for Web specials (there may not be all that many left for April) or the Estrella fares....second best bet. I would especially urge you to pre-book if you're in Spain anytime between 3 and 12 April. That's Semana Santa (Holy week) and many Spanish people take holidays then. It's a fairly straightforward process to book on RENFE, and you will get print-at-home tickets, but PM if you need any assistance.