Okay...let me first start by saying that I do not REALLY prefer Liszt over Chopin. I just made the title that way to catch your attention.
However, I will have to say that I prefer his etudes over Chopin's any day. And I must put to discussion how Liszt's music seemingly has that "mystical, ethereal" effect Chopin wasn't actually master of...I mean sure, Chopin was a masterful poet who could bring one's heart to tears in seconds...but Liszt had the power to evoke such powerful, particularly "nostalgic" emotions.
Take for example his Ricordanza etude. Or his Liebestraume number ONE (not the third!). Two really underrated pieces! They stand as one of my favourites, and few Chopin pieces in my opinion speak to me as closely as those two.
Or even Un Sospiro. Beautiful melodies, all of them - they don't possess the glittery, dramatic flourishes present in Chopin's "improvisatory"-sounding melodies, but they nevertheless captivate your soul. That's, in my opinion, the thing about Liszt. Just a few notes, but BOOM - straight to the soul. Speaks to you VERY FRANKLY.
I must admit though that Chopin of course also has advantages over Liszt. His ability to evoke melancholy is unmatched. I might say that Chopin's music has more of a "narrative" quality to it than Liszt's - I think that while Chopin's music can play a powerful, dramatic "scene" in your head, Liszt's music makes you remember the memory of someone really dear...just the memory, a picture, of him/her, period, and the whirl of emotions you feel for that person in that instant. That sad, rather lonely, but also reassuring, thought of remembering someone and what you did with them together, and how you loved each other so dearly.

So, what do you think? Do your thoughts coincide with mine, or do you have something else to say or challenge?