Onno created this image in 2002 to show the relative heights of QE2 and the new QM2.
I remember lots of discussion at the time, and the interesting thing for me is that the boat decks are at the same height. I think of this every time I'm on QM2 and look down to the water moving (slowly) past.
More info on Onno
http://www.modelships.info/debrisfield/onno_h_profile.html