my arrows at least the one im gonna shoot is on my string.field points may fly the same in your bow with wet feathers but with broadheads I think not. wet feathers may come rite back in steam but I dont know anyone who has a steamer or a tea kettle in the tree. so while you feather guys are not hunting in the rain or keepin your arrows covered up or your back at camp steaming them back in shape me and my plastin waterproof vanes will be in a tree in a monsoon shooting a huge swamp buck.
Try this (I have) - Take an arrow with feathers and broadhead, dip the feathers in a bucket of water and then shoot it at a 15 yard target (a bit further then the average hunting shot). You're going to hit real close to where is would hit if dry. Your not likely to ever shoot further in a downpour. I've hunted in the rain, using feathers, many times and have never experienced any problem because I had feathers on my arrows. All the other advantages far outweight any tiny disadvantage in a downpour.
As for steaming your arrow in the tree, I assume you were not serious. No one would ever have to. First, we do that at home before the hunt. If I damaged a feather while climbing a tree, it's still very shootable. If I damage a vane while climbing, I might as well throw that arrow back in the quiver. It won't shoot worth a crap.
The only real advantages of vanes are that some are cheaper, and most are slightly quieter.