You are correct that the additional shoulder strap attaches underneath the buckle, but it doesn't pose any issues.
I've put some seriously heavy/akward stuff in this bag and it's never pulled out of position. I also like that the Chrome strap tucks away and is hidden when not in use, but that's just esthetic's!

The Pac design does look better in theory for sure, but when I checked out the Pac bags in person they didn't feel as good to me personally. I also didn't like that the Pac "nylon" peice could slide up and down the strap.

But....... that's where personal opinion and subjectivity come into play, and I'm not really interested in discussing that over the internet.