Besides being much handier to change strings through the top load slot, I believe you get less wear and tear on your strings. As you pass a string through the hole in back end of your bridge you cannot help but rub the string winding against the edge of the bridge.  If the string is rubbed hard enough, you could deform one side causing damage (similar to the way you would rub scissors against a ribbon to curl it).  A deformed string may not orbit correctly, causing false overtones.   Also you avoid scratching the face of your instrument due dragging the string ball against the finish.