The main advantage is that content recommendations based on previously saved content are pretty good, especially for tech oriented crowd.
AI tagging feature like those in Pocket and Karakeep, in the first place, seems helpful. But months later, you will get lots of tags to handle. Content recommendation, especially if that only consider what we saved, can replace the tagging things I guess. I wonder how do you do this for free, though.
Also your HN/Reddit integration is what I'm looking for. The way I save things from HN so far in Karakeep is that I save the main article and add the HN url manually to the note.