Depends on the specific context.
I’d prefer to finish all the story content while remaining within the appropriate level bracket. Not so much looking for “difficult” content, but I don’t want it to be stupidly easy either; things just start to feel stupid when the next level up causes you to start one-shotting EVERYTHING.
Which, unless you take measures to turn off your XP gains at certain levels, is EXACTLY what happens when you out-level content too much. After some testing, I found out that kicked in at around +5 levels for a lot of the earlier content.
So yeah, you’re still fighting the game’s systems when you want to enjoy the game’s story content (even if it’s of middling quality for the most part); especially for older expansions.