It's hard to compare them directly. UE4 is and always was effectively a tech demo - everything is easy and fast to access and the map is pretty tightly packed compared to UE5.
UE5 is designed much more like a game that has adult content - it can easily take an hour just to be able to unlock character generation because that is unlocked by a quest that you get after running through the introductory area. Not only that, but UE5 has different combat, different UI, new mechanics, and approximately the same amount of content as UE4 but spread out over a much larger map. As a consequence, UE5 feels a lot more empty than UE4, especially to players who come in looking for quick access to various sex scenes.
A bit of UE4's content is accessible either directly or indirectly in UE5, but most of it is still in areas the developers haven't built yet in UE5. That means there's also not much overlap between the two aside from some of the major themes and such.
Also, UE5 currently has a lot more game-breaking, save-destroying bugs than the most recent UE4 version.
