I believe I want to buy one. Can't decide between .177 or .22 cal. I like .22 cuz I already have a Benjamin .22 cal. But OTOH I like the 1200 fps of the .177 What do y'all recommend? Next question: the Gamo mechanism is " spring piston". That the better mechanism, correct ? I believe the lesser (cheaper) guns are just spring, without the piston. Is that correct?