Hmm. I really don't think there is nearly as much of a dichotomy between musicality and technicality that some say. I think EVERY piece by a half-competent composer is musical. Liszt's "Grand Galop Chromatique" or "Mezeppa" or Balakirev's "Islamey" are very musical works. The composer put each note and expression marking in the optimal places to convey the exact musical picture he wanted to. And on the other side, these slow pieces mentioned in the original post are TECHNICALLY difficult. Having a wide dynamic range (especially between ppp, pp, p, and mp) is VERY difficult, and having a sense of touch to put accompanying voices "under the voice" while voicing the melody with a richer singing tone is also difficult. (Schubert Impromptu 90/3, Pathetique middle movement, Moonlight 1st movement, etc.)