The 125 Sniper comes moderated from the factory, has the quattro trigger and SAS vibration reduction system... But is larger/heavier by a fair margin. The 125 is a 30ftlb gun when unrestricted, not sure what they do for non FAC (sub 12ftlb) models to get the power that low. If it's just a soft spring (not destroked) the shot cycle might be a bit sluggish, not a big deal but it bothers some people. The Striker is a simpler model lacking a moderator, quattro trigger and the SAS system, hence the price difference.
My experience with Hatsan air rifles has been mixed. I've owned nine of them, still have five. Three have been flawless so far. One being a full power 125 Sniper (springer) in .22cal but it's not shot often...