I think the price difference is definitely because of the hurricane concern. Obviously any of the crusielines steer far away from the actual hurricanes, but it's possible (more likely than, say in January) that you'll experience rain, winds etc. Most people I know that have cruised at this time however, have no major weather related concerns.
The one thing you should know is that it is also more likely the ports of call will change. So, if you are dying to go to a certain place you may want to travel when the weather is more stable (though even then the CL can change/cancel ports). And finally, if your departure destination is in Florida, it's best to plan to go a day ahead (or more) to circumvent any potential weather delays.
RCI Sovereign of the Seas 2005
Caribbean Princess 2005
Carnival Paradise 2004