Wire has a sharper, louder sound than nylon, and tends to ring longer. Gut often has a more muted sound. Nylon strings are softer and quieter than metal, but easier to maintain and cheaper than gut. Pedal harps are usually strung with a blend of nylon, gut, and wire strings. Pedal harps are usually more tightly strung than lever harps.
Lever harps tend to have more resonance.
But even harps of the same size and style can sound quite different from one another, depending on who made them. If you want to know more about all the different kinds of harps there are out there, click here .