we have a nano cube set up as a reef tank in at school, its probably around 20 gallons, and nano cubes are bow fronts.
i hate this tank. when viewing from the front, unless i'm several feet away, everything is distorted and makes me really sick, the only time anything is ever perfectly clear is when looking at it from either of the sides (where its flat).
personally i would go for the flat tank because they're just plain easier to look at.