It would also depend on the likely weather conditions at that time of year.
Absolutely, yet even that can change within a period of days. As an example, we skirted a Category 1 hurricane on an August 2005 cruise from Boston to Bermuda, yet the ocean was smooth as glass on the return trip.
I'm glad we hadn't finalized our summer 2011 cruise plans yet. Thanks to this topic, we're also looking into Bermuda (again).