My vote is for Celebrity, we've been on the Millie twice and she is a beautiful ship, and recently refurbished.
Honestly, have not tried HAL, but others at work have and love it. They compare it to Celebrity.
We too, are looking at a Noordam cruise, a transatlantic out of Rome next October. The ship looks beautiful with a great spa and hydrotherapy pool (similar to Celebrity's Thallossotherapy). If you find out more, be sure to post! Have fun and good luck!!