Go with what you think looks cool. I don't think there is really any difference. Right now I am using 4" shield cut because they look cool, make no noise, and are plenty to stabilize my arrows. Longer feathers will stabilize quicker at the cost of a bit of speed. If your arrows are well tuned to your bow, you don't really need more feather. I like 5" or 5.5" with woodies because there will always be some variation of weight and spine with them, so more feather tends to straighten things out more quickly. Carbon or aluminum arrows really don't need much for feathers if they are tuned to the bow.
That was kind of a long-winded way of saying it doesn't really make a bit of difference. :D