Am I correct that D and S5 shift positions drive exactly the same? The only difference being S5 takes more shifts to get to and D has those wonderful eco lights and eco graphs (that's sarcasm, in case it didn't come through in writing).
I have never noticed any difference on my 14 or my 03. I always use the S mode and do not use 5th gear unless the speed limit is over 35. It is mountainous where l live and 5th gear just causes a lot of down shifting and riding the brakes down hills.
I believe D will give you the intelligent shift; engine braking, holding a higher gear. From what I've experience with S5 it doesn't do that. It could just be a situational thing though.