I have done both SAS and UA
I took SAS ORD-CPH
** Good service, didnt care for the food coices which are scandinavian (breakfast was yucky as I just wanted something continental). The plane was packed and I was in a middle seat in the middle section with a lot of Danes around me. Everyone reclined so not much room for me and didnt sleep all that well cramped in.
8 for service
5 for food
5 for comfort
6 overall
I took UA IAD-FRA and then SAS FRA-CPH
** decent service, food was okay (i think it was chicken or beef, which you'll find on many UA flights overseas). Breakfast was decent. I had economy plus which was a lot more room than SAS offered so I slept much better on that flight. Plus as a UA member i got my e-500 mile credits and lifetime mile credits. one thing to note, SAS did forget a container of bags in FRA and mine was one of them. I arrived Sat afternoon and they had it to me by sunday midday - but that can happen with any airline anytime.
8 for service
7 for food
8 for comfort in Econ+
8 overall