Hard solder does not pit as medium and easy do. See the photos below. I teach my students they do not have time to dork around using three solders. In the time it takes to decide which one to use where, they can have it soldered and finished. If a piece gets ran over by a car, the poor slob that must repair it, will not have fall completely apart as he, or she, heats it up.
Hard solder makes stronger solder joints.
If you want to know why joint the Silversmithing List and ask. If you learn to use a torch good enough to use hard solder for every solder joint, you are, of course, good enough to use easy solder, if you wish to. If you do not believe you could make this piece easily, you need my Online Beginning Silversmithing Class.