Not only does the Decent skin show more of the map screen overall, but it also displays more information at the same time (and looks better and provides more functionality).
In terms of the data fields in the stock skin using more space compared to the Decent skin, I did a mock up for you - I put the 3 stock fields over top of the 3 Decent fields - which uses more space? If I added the other information that Decent provides on the screen (date, time, speed and second-turn info), it wouldn't even be close.