Button knot would be more reliable, but the dyneema is so slippery we decided to use the ball... a plain knot might be the way to go.
There are plenty of knots with a good enough nip to hold in dyneema. As a class, lanyard knots might retain their shape under load better than button knots, but I'm partial to the form of a 2-strand 8-part button. That's what I put in my soft shackles.
