Your boat is almost always better on a mooring and/or on anchors than at the dock in a hurricane. Docks feel solid and reassuring in normal conditions, or even in pretty severe storms, but the difference in a hurricane can be storm surge. The photo was taken during Hurricane Bob with our boat at the time, Echo, on a mooring with anchors out in Cuttyhunk. Only three boats in the harbor broke loose, and they were all due to either inadequate mooring lines or too little scope. One boat picked up its mooring and dragged it ashore. If they had put out 50 feet of line the boat would have been fine.
Why were we there? Simple, the storm was predicted to go right over us, or very close, and the storm surge was predicted to be 10 feet or more. I think we had close to 10 feet. The fishing dock and the ferry dock were under water in Cuttyhunk. Four-wheelers and large propane tanks floated off of land and drifted by us. A small shack floated by, roof upside down, like a boat.
If we had been tied to the fixed docks everything would have been under water. Lines would have to be either impossibly tight, or terribly loose. Even if our boat didn't break loose or float off other boats would have, and they would be right next to us. Watch the videos from Irma of boats sinking in slips, tied securely to pilings and docks, due to collisions with the marina infrastructure or other boats.
Yes, if your are on a mooring or anchor your lines could break, and your anchors can drag. But, at least your boat is pointed into the wind and seas and it can have a chance. When tied up to a dock you are at the mercy of the wind direction and how well your neighbor has prepared, and how well the marina has maintained everything. But, get a 10-20 foot storm surge, and nobody is prepared. At anchor or on a mooring your boat has a chance. Add extra lines and extra scope and the boat can rise with the rising water.
Give your boat a chance in a hurricane.