While Asiana's seat is not a full lie-flat seat, they do not give these seats away, so while not guaranteed, there's a pretty good chance to have an empty seat next to you. And, no matter what, there will be only 1 seat next to you as the A330 they use is 2-2-2.

UA with the 777 will have a 100% full business cabin, 2-4-2 jammed in to lie-flat.

As for sleeping - for me they both have weak points - the narrow footwell on UA is uncomfortable, and the Asiana seat isn't quite long enough either. I really dislike the width on UA seats.

With UA, the restrooms, and almost everything else about the flight will be nasty. With OZ, they start clean, and they keep them clean. For me, there's no question - OZ. The flights aren't that long, but OZ is a bit longer allowing a bit more time to sleep if you take the far superior OZ meal service.