From my experience, playing Bach is harder than playing Liszt. The transcendental etudes are hard but thinking in 4-5 independent voices in his WTC is just impossible. I feel like practicing technique is easy but trying to figure out Bach is crazy.
I feel that's a popular opinion. In my opinion Liszt etudes are harder, most people don't do them justice because they believe that mastering the technique is enough and feel that they're "showpieces" which don't merit the same attention to detail as a Bach fugue.
Topic: Unpopular Opinion