Keep in mind that another term for "subsonic" is "standard velocity". I believe most of the match and target ammo is standard velocity.
One advantage for subsonic that I have heard is long distance. After about 50 yards, subsonic ammo drops below the speed of sound and starts to tumble. That throws off the accuracy slightly. Subsonic rounds start off below the speed of sound, so they don't have that problem.
However, The speeds generally quoted for .22 LR rounds are with a rifle barrel. If you are shooting from a 6" or so barrel, the High Velocity (Supersonic) rounds are not supersonic. So just about any rounds we shoot are subsonics to our Mark IIs and 22/45.
So I wouldn't worry too much about the distinction of Subsonic versus High velocity. Just find the ammo that shoots the best in your gun. I think that the Remington Subsonics shoot fractionally better groups in my gun thatn the Federal Lightnings, but since the Rems are twice as expensive, I don't shoot them much. Also, keep in mind that the subsonice do have less velocity, so they don't shoot as flat.