This is an interesting topic!
A couple of years ago I wrote down some keys and their qualities.
I tried playing around with phrases on piano and I had to go back to them for a second opinion. I simply used wrote words like sharp, mild, timid, warm, cold for different major and minor keys. I also checked what church modes works well, in what key, for instance I thought the phrygian mode came across best in C, F and G while Dorian worked best in F and Bb, also B but a little milder.
I think there could be some sonic qualities in different keys. You guys were talking about instrument range, some things were easier to play and also preferences from earlier listening or playing experiences. But what about science, is there some frequences that resonate in a certain way that makes them more clear/sharp/dull?
I thought about Bach’s WTC and his choice of melodies in different keys. Does anyone know if Bach had any thoughts on different keys and their sonic qualities?
I also reckon some keys have a better and clearer timbre in vocal music, like choirs, Eb and Db.
Take a look at this YouTube clip where she takes an example from Schubert’s Impromptu, comparing two keys.
Just to make things more complicated, she also mentioned in a comment that pianist may sound different because they play more or less expressively because of the tactile feel of the instrument on that key.