Hello
Probably like most people who fletch their own arrows, I have tried a lot of different styles and feathers. I always seem to end up back at the four fletch 4" parabolic feathers in helical. And usually three light feathers and one dark one which makes the spin noticeable as the arrow travels.
I think I like the fact that you just grab the arrow and it can't be placed on the bow wrong.
In my experiences I've noticed no difference in flight between the shield or parabolic feathers. I think its an appearance issure. Parabolic are just easier for me to get my hands on locally.
Dan