Sound quality is mostly subjective, not an objective truth.
Gut isn’t objectively a better sound than nylon, and concert tension doesn’t objectively produce a better tone than folk tension.
Some people simply like the sound of one over another. Some music generally sounds better when played on the one or the other.
Also far more than the strings go into producing the tone of the instrument. The construction methods, the woods used, the way the soundboard is shaped… there is no one element that can be pointed at on a harp to say “this harp uses X and that harp doesn’t, therefore this harp will sound better”.
You need to go listen to the sound of the actual harp itself and decide if you, personally, like the sound of the harp when playing the kind of music you want to play on it.
That is the only determination.