I personally love the powder blue, however I think the powder brown looks nicer in a tank as it contrasts against all the other colors and fish typically. Not sure off hand what you stock but the brown would be what I pick.
It was a tough choice .. I think they are both beautiful , but I ended up going with a powder blue , only because where I bought it was qt for 2 more weeks then the powder brown , was very healthy , about 3” max