You have many times more miles than required for two transatlantic economy class tickets. You definitely want to redeem through a USA based frequent flyer program, and probably fly on a USA based airline to avoid fuel surcharges, because econmy class fares are primarily fuel, fees and taxes. If you pay fuel surcharges on the award tickets there will be very little savings.

Please clarify what you mean by best flight experience possible. There is not much to choose between airlines in economy class seat pitch or width. What else would be important to you: nonstop flights, departure or arrival times, meals, in flight entertainment?