Originally Posted by
Metaluna
In the same vein as Sixy Fiver's comment, the low normal RD design is nice for bikes with bar-end shifters, since both levers get pushed in the same direction, i.e. pushing either lever down gives you a lower gear, and pushing up gives a higher gear.
The ideal set up with bar ends on a higher performance bike is to have two high normal derailleurs as this gets the shifters out of the way when you stand and hammer as you can sometimes hit them and cause an unplanned shift... on a touring bike you will sit and spin lower gears on climbs and when you stand up having a low and low set up gives you your lowest gear and points the levers down and out of the way.