I have always heard Deere decks rust through quicker in part because they are thinner and stamped which adds a lot of residual stress,i.e. energy to speed the corrosion. The other side is that the stamped decks have smoother flow lines so that the grass should not have the corners to end up in. Then of course some say you only notice it on the Deeres because the tractor lasts longer.
What i do know is that if the grass sticks on and stays wet it will rust - if it is always clean and used regularly it will not rust. If it is not being used it should be coated.