Subban may be better in defense but if both plays all 48 games, Letang has the Norris.Won't happen, Subban is better already. As for the trade one would think a prospect like Beaulieu would be interesting to the Penguins, they would also want a winger + picks coming back.#
But Letang is also two years older.
Now, if I have to choose between both right now, I would take Subban because he is more durable and will continue to improve.