I don't really like reading anything. If I had to pick, I think I'd lean towards rather reading flats, especially as the number of them increased. F & G, pretty similar, about as comfortable as anything. Bb & D, I like 'em both, about the same. Eb & A, definitely prefer Eb, not crazy about how A falls under the hands. Ab and E, much prefer Ab, do not like playing in E, will if I have to but would rather be in either Eb or F. Db and B, Db all day long. B is pretty, but I don't do enough in that key to feel comfortable playing it let alone reading it. And Gb & F#... I would prefer reading neither of them. LOL!! In all honesty, though, I play in Gb / F# way more than I play in either E, A, or B... by ear. Pretty key and lots of black key stuff that's easy to play. 🙂