crinkles, what sort of target shooting, and under who's discipline ?
NRA will only let you use .22LR in competition, and the subsonics are better for wind drift at the up to 100 yard ranges. Supersonics drift a little more, but are still OK. The .17 rimfires can't go to an NRA competition.
SSAA allow more leniency, but don't have things like the Queens etc. if you get hooked.
If you take a magnum to the range, no-one will be your friend, as you'll scare them (seriously, watching people on the range flinch when a magnum goes off at a .22 event seems silly, when they don't at a centrefire event).
The .22LRs seem generally more accurate, and are way cheaper.
If you were going to be a fox shooter, I'd suggest the magnum. Gave a few boxes of LR qikshoks to farmer mates, adn they reckon that they are nearly as good as mags on foxes and roos.
Targets and bunnies, the LR every time.
Hitting a rabbit with a winchester subsonic, and hearing a solid "thock", and not having everything within a half mile run away makes a morning more complete.