Hola Ignacio,
Well, to me Aviles would be pretty for sentimental reasons, since my abuelo was born there. The photographs that my uncle took showed a very nice town, about the size of its sister city, here, St. Augustine, Florida. Of course, this is very subjective, as you said. Yes, I am sure there are prettier cities in Asturias. My Mother was born in Ribadesella in the Atlantic Coast and that is a very pretty beach town, but I am sure the cost of housing would be more dear there.
Here are a couple of photos that I borrowed from the net about Aviles,
Here is a view that I like of Calle Ferreira leading to the Plaza
.
About the costs quoted to my uncle, I believe that my uncle will have our cousins help him build his home. One is an albañil (builder) so perhaps that is where the cost may be a bit less, and his son is an architect, so that will help as well with the costs. But I think the savings will be because he is building a very small house.
Regarding the medical system, my uncle was positively impressed about the way the hospital treated my aunt,who had a heart attack while in Aviles. He said the hospital staff was very efficient and professional. Also the cost was very reasonable, he was
impressed about that too.