These numbers don't really tell the whole story. Keep in mind that the hatch volume (with seats up), reflects the volume all the way to the roof. This is good for carrying taller items, that you would never be able to fit in a sedan trunk.
However, I believe that if you are looking a overall surface area of trunk space the sedan is bigger. I believe someone made a comment about being able to fit a set of golf clubs in the back of a sedan, but with the hatch, you had to remove your driver.
That being said, I am going to be purchasing a hatch. I like the look of both equally, but what bothered me about the sedan was that while the trunk area was larger, the trunk door was so small. I can't fit my hockey bag into the trunk because it won't fit through the opening. I also prefer the versatility that the hatch offers.