Well, considering that that information is from Wikipedia, it has to be true right? (sarcastically)
And now that I finally find a paper that I printed off a long time ago, I must agree; and therefore i withdraw what I said earlier about "Un Suspiro" not being an etude. I refer to fact that it was the third written from Liszt's Trois études de concert.
Regardless, to the original question stated a long time ago, I believe that it isn't a matter of being and Intermediate Amateur or not. Those are just words, I have been playing eight years, consistently, but to a virtuoso pianist (such as Wilhelm Kempff) I would be considered a beginner. Therefore, my answer to the question is to pursue both. But only work on one at a time. The way in which you would do this is to work on whichever piece you wish to first, for about, say, three months. and then let it go for three while you work on the other piece. And keep doing this in three month increments. Occasionally, during each three month period, pull out the piece your laying off, and play through it once or twice during the second month. This way, you keep switching styles, and therefore you are challenging your brain to think about the music much more than you (it) would normally. If any of that makes sense.