I haven't shot either one but have held the GSG at the store. I was amazed at how much it weighed compared to how it looks. My mind thinks it should be like an airsoft, but actually feels really good. I vote GSG.
I have the GSG, first gen. Paid too much for it when they were the "NEW" flavor of the month. Not knocking it, it's a fun gun and reasonably accurate, but would have preferred $300 used to what I paid. No knowledge on the SU-22, other than the old Soviet jet.
I have the GSG on layaway here. That telescoping stock is real lame and loose if you pull it out all the way. Luckily it also has the the solid stock for me to put back on and 3 magazines and a red dot scope with it. I just happened to see it when I picked up my wife's B'day ring a couple of weeks ago. Other than the lame stock, it's a very nice .22.