I've had buttons crack and shatter while fighting fish and the button gets hung up on the edge of the hole. The problem then is rerigging a new button when it's -10 with a 15 mph wind. All the fun comes out of the sails about that time.
I used to use the little bobbers but the ones nowadays are either too big, or the tiny ones are cheaply made and break or the wire bends easily. Slip bobber knots set into the dacron and don't move once tightened. Not an option unless I'm fishing the same holes every night, and I'm not.
Slip bobbers and the toothpick with spare toothpicks is the way to go. You never lose the bobber. Just make sure you put the toothpick in the bottom of the bobber. That way when you bring the line up while fighting a fish, it won't snag on the bottom of the ice.