The Hudson landing was accomplished with Normal Law active due to the decisive action of the crew in getting the APU going. Had they not done so and relied instead on the RAT, then the ditching would have been in Direct Law, the protections would not have been active, and it would likely have eroded the safety margin somewhat.
That said, I'd take issue with use of the term "easy" regardless of the context - no water ditching could be considered that based on the things I've read and learned over the years.