Since it hasn't been posted yet, here's a full list of the changes. Range from "anecdotal" to "OH GOD WHY DIDN'T I HAVE THIS" :
https://www.thegamer.com/everything-new-dragon-quest-xi-s-definitive-edition/
Just don't read it if you're currently playing a non-Switch version, it can be quite disgusting to see what you miss.
Some excerpts :
- Fun-Size Forge Can Be Used Everywhere
- Orchestrated OST (!!!) + DQVIII OST
- Photo mode (I'd have used the shit out of this , game's gorgeous)
- Party members are now viewable in the overworld (+)
- Cutscenes are immediately skippable (definitely would have shaved a few hours of playthrough, sometimes quitting and reseting game was faster than waiting for everyone to be killed)
- Summon horse from wherever (useful)
- Running over monsterd with mounts grants more XP (+)
- Some real good new rideable monsters
And the worst offender of all in my opinion :
- Battle Speed Selector - this is modern RPG 101 Square, you even offer that on most new titles and remasters !
And I omitted some more spoilery ones, check the list.