When we left Kauai, we had to slog directing into the wind for the first 20 miles to get out of the influence of the island. The island influence is due to the mountains, volcanoes, and shallow water around the islands that cause confused seas, steep swells, and often strong and/or shifting winds. Heading directing into the wind we tried to get the Jib up to steady the boat. Raising a sail will always make for a smoother ride even when motoring.
We had to deal with the rocking and rolling of motoring. How you power boaters out there deal with this I have no idea. In the the video below is Go For Broke leaving Kauai under power (motoring) with no sails set.
The video below really shows the advantage of "motor sailing" as opposed to just plain motoring. While departing Oahu we were motoring-sailing across the swell in the video below and the boat is still comfortably level.