Even if it does not begin with 'E', I really like Walter's name for the new android. We'll see if Scott gives us an unexpected twist. If there will, I do not think it's related to a third robot. I would seem too many in one movie.
And about the technology of the ships... As others have mentioned, it seems logical that the Prometheus is more advanced than the Nostromo. That it is the most expensive ship ever built is a good excuse to justify holograms and cleanliness. The Covenant, so little has been seen of her, seems to have a more tough and austere appearance, close to what we saw in the movie of '79: