SHields rule, parabolics..... I started shooting shield cuts because the look traditional to me. I keep shooting them for the extra surface area for control of arrow flight and I use the taller fletch as a second anchor on the tip of my nose.
If you stand a bit forward of a shooter and listen to identical arrows, on fletched with shield and one with parabolic, there is a difference in sound made during flight. The shield cut fletch make more noise, not enough in my opinion to change weter a shot hits an animal or not. But yes they are noisier.