It's been a couple of years or so, but I owned the Kowa 884 and S2 briefly at the same time, and compared them several tmes side by side. Out to about 40x I could tell little to no difference. Both were very sharp to the edges. The closer I got to 70x, the better I liked the S2, as it maintained it's sharpness a touch better. When there's no mirage, the S2 is better at max ranges. I have never seen the 774, but I wish Meopta would come out with a 65mm S2 type spotter.
