I've heard the piano solo version before. It's different. What they have in common is that nostalgic feeling. I see this theme (in both versions) as a track for a film, for example. You know in the movies the music is presented in different forms. Nice.
It's emotive and sweet. I don't see a clear structure in the piece, as it is always moving forward. Perhaps it was your intention, but I believe that, even in short pieces, a structure is good. If you plan it, you can do many more things with the same material.