I think the difference as I see it is that Twitter/X is oriented around increasing levels of "engagement" and encouraging contributors to focus on going viral in hopes of going even more viral by reaching the "For You" feed.

Bluesky seems a bit more like a 140 Characters mashed with Reddit with subtopics/submods of feeds as the focus. Also it seems to highlight the custom feeds feature which you can manage yourself. Twitter/X has such features but for the most part you are nudged away from these to improve "engagement" metrics. That said its highly possible that could change over time based on the long term vision.