Most Technically Advanced Composer: Alkan vs. Liszt?

The difficulty of a composer's piano works isn't necessarily related to their technical abilities - Villa-Lobos was a very poor pianist, despite writing a lot of difficult music for the instrument (e.g. Rudepo�ma, Bachiana Brasileira No. 4). Both Liszt and Alkan were great virtuosi, by all accounts, but we don't have any recorded evidence of their playing. Why should we pick one over the other, without any basis for comparison? That's just empty speculation.