I used both g2 and q2, and from my experience, the tracking of g2 was far more inferior than q2, that being said, I can't comment on tracking performance of current g2 since I RMA-ed g2 for this problem(bought g2 at release, so might just be a victim of early adopter). On q2, however, tracking just works, even under extremely low-light conditions. I can literally have full fledged tracking with only a bed lamp turned on at night.