Carabiners are standart connectors wich are super intuitive to use, contain no loose parts, and close automatically. The downside is that they force is loaded very unevenly on the two sides. Due to their slight flexibility, Cyclic loading is a big issue when using carabiners in slackline applications, so they are not suitable for usage in the main load path of your slackline setup.  But they do a good job in mutltipliers, fixing working ropes while rigging or for backing things up.