I bought this one in the M/l it is longer than s/m but not that much larger. If you are on the cusp of size go up a size if tall and go down if you 164cm and under.
They are very versatile easy to throw on and comfortable, just like a nightie but with a fab design that you can wear to shops. The dresses would be great for summer holidays for beach, pool or even camping. I would rather pop on this dress than a sarong over my swimmers. I think they would be great for travelling also, no need to worry about creases.
Best feature they have pockets, yep just have to remember to empty tissues when I wash.