My experience is neither the V6 nor the V8 have decent side bolsters nor decent leather seats. The V8 Rspec seat leather 'sags' with minimum mileage and/or age. Seats in the 2013 V6 do not have anymore or less bolstering than the V8 Rspec. You would expect the Rspec to have some performance aspects to them. At least the 2015 has a much improved seat design, and the 2015 5.0L has power side bolsters. Regards.
The V6 w/out tech package has vastly different seats. I much prefer them to the V8 "ultra premium" leather seats...... the V6 has a firmer seat and side bolsters.