Fur Elise is much simpler. The melody is mostly a single line that crosses over from bass clef to treble clef. There is minimal simultaneous left and right hand interaction. Moonlight Sonata has a denser structure with more lines of notes per bar.Is Fur Elise hard?
The full version of Fur Elise is considered reasonably difficult, broadly an intermediate piece around grade 5, but a shorter arrangement of only the famous section is often taught as well. This is much easier, suitable for late beginners, but still requires some foundational skill to perform well.