I personally find the piano more difficult. My hands are well set for the harp, and the spacing of piano keys is much wider. I was never physically comfortable with some aspects of playing, and never learned that much in the way of using real technique on the piano. I do find, however, the harpsichord to be much easier, as the keys are spaced like harp strings, and the responsiveness is similar. But, boy, do they need tuning. We have it easy by comparison.