If you're in big water (outside, in following, breaking seas), it's nice to have the extra power, even if you don't usually need it. If you never get in that situation, stay on the lower or medium power end, but if you could ever be faced with outrunning a breaking following sea, you need to have the max power to stay on the back of the sea in front of you, to avoid broaching or pitchpoling. You need to have the power to stay out of the trough.