Kingdoms of Amalur is a bit of both, but mostly a disaster
Each area would scale to your level when you enter, then stay that way. So you start an area, it's a challenge, then by the time you're finishing it up you can feel that you've gotten stronger. Sounds great, right?
But two things went really wrong with it.
1. If you weren't aware of how it worked, or didn't pay enough attention, you could lock the level of an area just by passing through it briefly. Then when you go there again 5 levels later to actually do the quests, it would all be super trivial and boring.
2. There were caps to how high each area would scale, and it was really easy to blow way past them just by doing a majority of the content.
Result was that if you wanted to do most of the content and didn't want things to get too easy, you had to put an unreasonable amount of effort into not out-leveling everything