Suggest you consider combining your 2 basic options, especially IF you can break the journey for at least one nite on the westbound. EDI-EWR is quite quick actually, you can go into the city for a nice dinner and then sleep and not have to worry about rushing for the trans-con connection the same day. For the return, the UA E+ would make the most sense to me: the best chance to sleep en route at a reasonable price -- but as a West Coaster myself, many of us strongly dislike having to change at East Coast airports eastbound, as it requires leaving a.m. as oppposed to p.m., meaning you save time and gain most of a full working or relaxing day on date of departure. Seems the split-carrier ticket should be easy to set up if you do decide to do that.