I am a bit sceptical with the premise that the older ship are inheritently more stable. There are numerous stories that both of the original Queens were big "rollers" in seas until they were fitted with Denny Brown stabilizers. Other liners like the Stockholm, still in service although severely altered, have had appendages added to the hull to aid in stability. The IMO is the policing agent now correct? I wonder what standards, if any were in place in the 20's-50's regarding the stability of ships and if the standards have been tightened up as engineers have learned more.
I know from personal experience that, at least on small craft, the boat usually can take more of a roll than its occupants can comfortably take. I suspect that is the case of the old liners as well. Although they rolled in seas, with out stabilizers, I suspect they could roll substantially and still right themselves. I have a book in my library "Seaworthyness, the Forgotten Factor," by C. A. Marchaj. It goes into detail on stability primarily in sailboats and its effects on safety. I recall him mentioning the Fastnet racing disaster, where
Drum was overturned, turtled. After the disater and the ensuing investigation, it was found that some of the sailboats are/were actually more stable upside down in the water.
Regardless, QE2, with her extended foredeck and lack of windows has by far the advantage over any cruise ship at sea now, except one, QM2.