At higher bitrates than 128kb/s it is hit-and-miss whether a particular file will play, in my experience. Sometimes they do, sometimes they don't. (It also seems to vary from one client to another.) So I would recommend using 128kb/s to be on the safe side.
Also, although many of us (myself, for example) can hear the difference, many don't pick out the deficiencies in 128kb/s quality - especially not when playing a game where other sounds are layered beneath the music. Just a little silver lining to the cloud.
