From my experience, the area more or less around Gander, NF seems to consistently bring the seat belt lights on with a few bumps for a while. It appears to work the same way either east or westbound. YMMV.
Far from the worse turbulence I've experienced, however. That would be over Iraq, circa 2003 or so. And probably a few other times. But I'm getting old and the memory is getting feeble...