I will say, if you do go down the route of buying your own Renfe AVE ticket, the Premium ticket comes with seat selection, unlimited free changes, same-day change, a 95 or 100% refund if cancelled, and an on-board premium meal designed by a Michelin-starred chef that Comfort customers have to pay 22-25€ for.

All that alone, especially if you're a train fan as you say, might sway you. I can definitely vouch for the premium meals, having had a delicious one last night on an Alicante–Madrid AVE (I was booked in Comfort and pre-ordered a cheaper meal box, but it wasn't loaded so RENFE offered me a premium meal in its place as service recovery).