I use feathers myself. They just seem to fly truer and quieter. I would say that vanes are definately more durable though, but it shouldn't make that much of a difference if you are going to use a drop-away.
My rest is a Trophy Taker drop-away and I don't have a preference to cock feather. I did however take some digital video with my camera as I was shooting to make sure the feathers cleared the rest as I released. They did every time, but thats not to say that every drop away rest on the market is the same. Once you decide on a rest and your fletching, do some testing and tweaking to make sure you're getting total fletching clearance.
CRITRGITR