If you can’t decide- apply to both (plus a wider range of matches and safeties) RD and don’t contort yourself into a knot! ED is for a clear first choice which you obviously don’t have right now which is perfectly fine.
In my experience, “stress culture” and competition is more about the student and less about the institution. If you are vulnerable to stress and find competition grinding- it’s OK to find other schools which have a reputation for being more laid back than these two. I know kids who have found one or the other of these “stimulating” without being stressful, but neither is located in a bucolic setting which is conducive to relaxing strolls through the nearby woods to contemplate nature. So if you want “bucolic”- find another school!
Wharton is Wharton and Arts and Sciences is not Wharton. This is fundamental. You aren’t going to be a Wharton student.