Hull speed and hull design mean far more than displacement. For instance: 30,000SHP is sufficient to push your 1000' containership along at something over 20 knots, while it takes upwards of 120,000SHP, and another screw, to push the same vessel at speeds over 30 knots. Speed costs money, how fast do you want to go?
“Scientists are people who build the Brooklyn Bridge and then buy it.”
Wm. F. Buckley, Jr.