Here ya go.... Here's a good look at both feathers and vanes.
Feathers give me 272 fps, an FOC of 12.93 and K/E of 67.86%.
Vanes give me 267 fps, an FOC of 10.78 and K/E of 67.77%.
Which ones more accurate? Feathers by far. I mean, the vanes are great and give me nice groups, but the feathers with the right helical fletching are unbelievable!

Heck, when I first got these arrows from Hunters Friend
www.huntersfriend.com I went to an indoor archery range and tested them out against each other. The feathers were so accurate, I had arrows touching at 20 yards and even ruffled the feathers on a few of the arrows!
I'm shooting feathers and won't go back (unless it's raining - then I'll shoot the vanes).