I would think both of these will give similiar power. My OS 108 turns a APC 16x6 at 9k on 5% at sealevel. I believe your prop selection is more important for speed/power and you should be looking for great throttle response in the mid range. Weight is a smaller issue as is size. Its hard to beat the OS 108. A club member had one in a 1/4 Cub swinging an 18x6 inverted. It was great! I do love 4 strokes though.

Carl