When we were deciding on our QE2 crossing a few years ago, the clincher for us was the length of the days due to the multiple time zones we'd be passing through. On a westbound crossing, you'd gain an hour a day for five days; on an eastbound crossing, you'd lose an hour a day for five days. We went with the westbound route, and having five, 25-hour days was nice.
Good question on the Gulf Stream current, though. I have noticed on our several Bermuda cruises that the seas were usually calmer on the way to Bermuda than back to the US -- with a couple of exceptions.