Hello,If I were you I would go for Op 27 no 1. Of course this is a completely personal opinion.IMHO op. 48 no 1 is the most difficult one from your list. The required skill set is also vastly different from op 55. nr 1. Op 48 no 1 is not to be underestimated.Op 27 nr 2 is more specific I would say. Hence my "proposal" which I repeat is purely a personal opinion but hey that`s what you asked
What about the Liebestraum no3? Is it truly as difficult as people make it out to be?
Yes, the Liebestraum is hard. Both of the cadenzas are insane. The rest is fine if you can get a handle on playing the melody line with your thumbs. I learned about the first 40 seconds, and did not find it hard. It's the cadenzas (especially the second one) which are massive trolls.