One thing I like about both expansions, is the whole 'pack of people traveling together'-theme.
Minor spoilers for both HW and SB:
In HW it was the WoL, Ysayle, Estinien and Alphinaud in particular, like that evening around the campfire before they approached the dragon to degotiate. SB does the same thing with the WoL, Lyse, Gosetsu and Hien - mind, both the expansions had other characters for parts of the journey, but these are the ones that stuck in my memory the most. And both have a narrator for every part of their journey. I really like that!