I have recently been twice on the left coast version - Long beach to Catalina. That's about 30 miles. Took the Miracle 15 hours; the ferry does it in 1-2. On an aft facing cabin, its apparent the props, when running at all, are not churning up a wake at night. I only figured it out on my second voyage: For those extra hours, the bars are pouring and the slots are spinning. That's fine with me- I like my nights at sea.
I am told that QM2 can make NY from Southampton in 4.5 - 5 days, rather than the scheduled 7. But nobody wants that.