Barcelona - Madrid through the ave is great.

Paris - madrid with high speed train is also good but you have to book tickets early in order to get a sit

<<I'd rather spend 8-10 hours on a night train than vaste half day on a high-speed train>>

Personal decision. I'd rather waste the day on a high-speed train. Otherwise, I'd be checking into a hotel and wasting half a day catching up on my sleep.

"Personal decision. I'd rather waste the day on a high-speed train. Otherwise, I'd be checking into a hotel and wasting half a day catching up on my sleep."

You're right, it's a personal decision, but at least we shall have the choice. There are more than enough travellers who prefer night trains to be able to run them profitably as recent developments in Central Europe(ÖBB's Nightjet success story) have demonstrated it.

When I take night trains I can't always sleep well, but I could always enjoy a full day sightseeing after arrival before going to a very good sleep in the evening.