I have to say that I was in Soldeu last New Year and had a fab time.
There are loads of runs for beginners/intermediates and the area is all linked so there is a lot of distance you can cover if you want. I will confess that there are a couple of flat areas near to the gondola station in Soldeu but selfishly I'm a skier so I don't view them as a problem
I have a few friends who have been to Pas and Soldeu and they enjoyed bth although they admitted that Soldeu is "prettier" (Pas is a concrete town pretty much).
Soldeu has a fab apres ski and in my opinion I don't think you can go wrong with Andorra......