I tend to do both. If it is a simple quilt and I want to finish it I use one piece.
Sometimes I have to piece as the colour I have only comes in small pieces. Not my favourite as I also plan it goes exactly in place and it takes ages to sandwich correctly.
I hate wasting time because nobody notices the time you took over matching the two. I did one for a show and put it in double sided. I heard some ladies say.@you would have thought she had made the seams straight' If she had thought the other side had wavey musical stave and the seams matched the black lines.
Do what you want please yourself.