The only one that seems to change how the game plays (instead of between game character modification) is the staff rule which suggests that the wizard won't be in a position where they cast a bunch of spells and then get killed when a cat swipes them across the ankle.
Personally, I jettison all XP rules from all games and use my own (except for Chaosium's BRP variants), as changing them has zero effect on gameplay, but I can see how people who enjoy TFT's experience rules would not like the change.