The chop at the Buzzards Bay side has been very noticable after the bucolic passage through the Canal.
When we went through before Irene, there was a "last train out of Paris" (Casablanca) feel as boats fled away from the impending storm. It sure made me think we were doing something wrong when the exodus of big, proffesionally crewed boats all seemed to be heading the other way. ;^)
THe tidal variations of the 9' plus Cape Cod side against the 4' or so Buzzards Bay side. Add that to the wind effects on either side and I think you get the mix master on the Buzzards Bay side.