When I fly, I'm stuck in Y because it's all I'm allowed to buy. UA is my airline because I'd rather be in E+ than other airlines' Y on these long int'l flights. That said, I'd try to route the overwater segments on 777s rather than 747s for the reasons cited above.
These are long flights. Pack your noise canceling headsets (I use QC2s), inflatable neck pillow (inflatable is key), reading material and melatonin (or something stronger), and take advantage of the free liquor. Don't expect a lot, but admire the fact that the journey won't take months and no one will get scurvy or abducted by pirates. UA will get you there safely, and more comfortably than many alternatives (though not those closer to the front of the plane).