I've noticed that people running a 55 seem to like lower air than people running a 50. Even with tires of the same width. Does the shorter sidewall flex more or less
As Nolton says, it's personal and determined by brand more than size however same brand and same model tyre would give you a conclusive, lower profile gives stiffer side wall providing less flex and firmer ride. People run lower pressure to soften ride and increase flex in this circumstance but tyre is designed to work differently.