I put together an 11" AR-15 upper yesterday and today took it to the range, along with the AUG.
As you can see in the pic, with the stock opened the AR is a couple of inches longer despite the 5" shorter barrel.
According to my Chrony studies, the 11" barrel loses about 150fps compared to the 16", so the AUG has a clear edge in that department as expected.
So you get more punch in a smaller packet. Obviously nothing new to anyone here...
Otherwise it's mostly a matter of taste and a bit of an apples and oranges situation maybe. So best to have both. Shorty ARs are just fun
"Making and Shooting of" video of the 11" upper here