Quoting "Ian Jackson" <ijackson@chiark.greenend.org.uk>:
Personally I wouldn't trade a 4h train journey for a 4h coach journey [...] and of course I will be arriving in Madrid by train anyway.
Same for me: Night train Berlin-Paris, visiting Louvre and Tour Eiffel; in the evening Paris-Poitiers and the night train Poitiers-Madrid, and finally < 4h to Caceres.