They are more forgiving because they can flex, if you have any kind of contact on a plastic vane it will mess up its flight. Feathers are also more durable, you can cut big chunks out of a feather vane and it will still fly just as quiet and straight as when it was new. do that to a plastic vane and it's ruined. Plastic is supposed to hold up better when they are wet but i think that is more myth then reality. as long as the feather isn't completely saturated they still fly just fine. I think they stabilize a broadhead better because they create more drag, inch for inch when compared to plastic.