I shoot GSPs in bullseye competition - I have one of them in .22 and one in .32 S&W, and several of the other members of my team have them as well. They're magnificent guns - very accurate and very, very dependable. I have never had to fire an alibi string in .22 gallery competition and I'm one of those guys who doesn't believe in cleaning a .22 target gun more than once a season or so.
I'm less familiar with the Pardini, but have heard nothing but good things about them. The Pardini has more of a "dropped wrist" grip, which some like and others don't. I believe the bore axis is lower relative to the grip in the Pardini as well, which should reduce felt recoil and muzzle flip. I think the choice comes down to what feels best for you and you should try to shoot both of them before you make a decision. I don't think you can go far wrong either way.
You may also want to take a look at the new(ish) Walther SSP, which has some of the ergonomic advantages of the Pardini. I think the bugs are pretty well worked out of them by now.