I would go with the Canon G15. Not only you gain the OVF, but you also get a wider aperture and closer macro pictures. That should make up for the 140mm vs 200mm equivalent lens. Other advantages are: the weight, ISO range, 1080p frames/sec and 24p support.
One debatable subject is the continuous shooting. I read both manuals and found that Nikon P7700 shoots a max of 6 frames at a speed of 8 fps, while Canon G15 shoots a max of 10 frames at a speed of 10 fps.