The kind of pressure you like from your blanket depends on who you are. If you love deeper pressure to give you that calming effect, then you should get the 20lb weighted blanket. It is heavier since it has been weighed with either more beads or stuffing.
It is beneficial if you need intense sensory pressure to calm you down. YNM ensures that the beads in the 20-pound weighted blanket are evenly distributed since a mistake with this can lead to issues with the user.