In my opinion and experience, Mark X should be clearly quicker. CL9's tranny is a massive let down. Tall gearing, due to being 5 speed, coupled with peaky power delivery and useless late VTEC also hurt.
While on paper Mark X weighs about 100kgs more, but it has very nice midrange power and 6 speed tranny. I recently drove a friend's Mark X which is in great condition and it was quick.